Sport
Are they the best or are they simply the biggest? Fitzgerald’s research is helping Kerry to identify young talent
by Adam Moynihan
Fascinating academic research by former Kerry captain Fionn Fitzgerald is helping Kerry GAA to more accurately identify senior stars of the future.
Fitzgerald, a lecturer at MTU Kerry in Tralee, is currently undertaking a PhD on the topic of the maturation effect in underage sports. He has found that although players in Kerry’s development squads might be the same age and play at the same age group, some of them get their growth spurts earlier than others. These early maturing players can, in effect, be much older than their peers from a biological standpoint.
In simple terms, Fitzgerald has examined the advantages early maturing players have over their teammates, and the effects this can have on all of the players within the system.
“We knew that age was an issue,” Fitzgerald explains. “We had explored this before in football and Gaelic games and we found a huge age bias (e.g. players born in January have an advantage over players born later in the year).
“But we also suspected that early maturing players were getting a lot more opportunities and were dominating sport. We then went about investigating if that is, in fact, the case.”
In short, that is precisely the case. The Dr Crokes man discovered that out of roughly 180 players in Kerry’s development squads, only one was categorised as 'late maturing'. The rest were either 'on-time' or 'early maturing'. The stark figures clearly indicate that coaches had been selecting players based on performance – which at underage level can often correlate with physical attributes - rather than potential.
“Scouts and coaches in all sports have been picking for winning, even at that level. That kind of narrowmindedness is magnifying the maturation effect. We have found that when we worked with the development squad coaches for over a year – and in fairness they really supported the work and bought into it – they got a greater understanding of the subject, and they kept more players in the system.
“They were less likely to dismiss a player as being ‘not up to it’ or ‘too small’. They were trying to keep an open mind.
“It's just very hard to make a conclusive call on a 14-year-old. This maturation aspect is not everything but it’s one huge factor that clearly clouds coaches’ opinions.
“You normally see more of a level playing field at minor than you would at U14. But the problem is that some players have already dropped out by then. And the players who were the main men, playing in central positions all along, they’re probably struggling because everyone else has caught up with them physically.”
BIOLOGICAL AGE
Instead of just going by chronological age, i.e. the player’s age according to their date of birth, Fitzgerald and his peers also use a metric called biological age. This involves measuring the player’s height and weight, as well as the height and weight of their parents. This data is then used to predict where the player is in terms of their physical development and where they will end up as an adult.
Being able to pinpoint when a player might be in the middle of a growth spurt is also helpful when it comes to injury prevention; players are more susceptible to injury during this period of their lives.
Some of the physical differences between players who were born in the same year are incredible.
“We found players at U14 level who were at 100% of their adult height. In other words, they looked very physically developed, because they were, but they weren’t growing anymore. Then we had players who were 85% of their adult height, so they had a huge development ahead of them.
"We had one player who was 40kg and another was 95kg - at the same age group. You’re into a ‘men versus boys’ scenario."
“We found that in some of the squads there was five or six years of a difference in some of the players, biologically speaking. That’s a huge gap. Biological age is probably a more accurate age to rate players on than their chronological age. Your date of birth means nothing really at that point of your life.
“So, who’s actually benefitting from the age groupings?” he asks. “Is it the early maturing players or the late maturing players? Ultimately, it seems to be neither of them.”
BIO-BANDING
One alternative to the traditional age groupings is a practice called bio-banding. This entails arranging players based on their biological age, so that early maturing players are placed with early maturing players and so on. The method has been embraced by clubs in the Premier League and New Zealand Rugby amongst others. Under Fitzgerald’s guidance, Kerry GAA have also implemented it in their development squads, albeit as an “adjunct tool” rather than as standard practice.
“I learned everything I know about bio-banding from the Premier League,” the Killarney native says. “The likes of Paudie Roche over at Arsenal and people at Southampton and Bournemouth gave me an insight into how clubs do it over there. They might have one week every month where they do bio-banding.
“What we did with Kerry was we trained away normally for a while and we tracked their maturation. Then we matched players in training, and then later in games, based on their maturity. We had Kerry South and Kerry North development squads and there were two different teams: an early maturing team and an on-time maturing team.
“They played in training and small sided games against each other, and then they played a full 15-a-side game."
The results of this experiment were informative to say the least.
“The early maturing guys who would normally be able to go through the centre and use their physical strength, they struggled an awful lot. From a skill execution point of view, they found it difficult because they were all at the same physical level. The team play wasn’t as good or as cohesive because they’re used to playing more individually.
“On the other hand, the on-time maturing players, they found it brilliant. Normally they might be playing in the corner, not getting much ball, and when they do get the ball they can’t take on their man because he’s bigger than they are. The skill levels were quite high in this game with a lot more interplay.
“The coaches also found that this game was relatively noisy because these players normally don’t take up leadership roles, maybe because they have less of an impact due to their size. They were suddenly talking more so it seemed to have a positive effect on their confidence.
“Both sets of players found it to be a positive experience. The early maturing players found it to be a big step-up in standard and the pace of the game was fast. They got exposed to a different challenge, a more appropriate one.
“The coaches loved it because they saw players in a different light. They saw players who they thought were excelling, struggle when they were put into a mature-appropriate environment. And they saw less mature players getting a chance to shine. It gave them a different slant on their players.
“Grouping players based on their age is flawed, but it’s not to say that we don’t do it either. It’s not practical at all to say, ‘let’s scrap the age groups’. But it is useful to coaches and parents to understand what really goes on.”
CROKE PARK
Fitzgerald’s work has attracted interest from the GAA at a national level. Croke Park have been in contact with a view to experimenting with bio-banding in other counties during the summer.
“It’s not like we’re replacing the chronological age groupings but maybe once a month squads might do bio-banded training sessions or games. Or they might play bio-banded matches once or twice a year to give the players a different challenge.
“It's an appropriate tool to magnify the effect of maturation. A couple of counties who are starting to embed practices around growth maturation might look at playing some challenge games against one another to scale it up a little bit. Rather than it just being done in Kerry, maybe they’ll get to play another county. Cork is another county where we got a lot of our maturation data last year.”
Over the course of his research, Fitzgerald, who recently launched a new youth athletic development programme called the Kaipara Academy, has seen a similar trend across the board.
“We found the same thing in GAA development squads, in Irish soccer and at Premier League clubs: their talent systems are dominated by early maturing players. In Kerry, there was only one late maturing player out of 180 in the whole system. And that particular player was Messi-like. In other words, if you’re late maturing, you have to be something special.
“That’s the issue with the effect of maturation. Potentially there are players who may be less skilful but their physical prowess is skewing their performance. Equally there might be players who have lots of potential but because they won’t mature physically until later, they get overlooked.
“This is not just a problem at county level, it’s also a problem at grassroots level. More research needs to be done here but it’s quite notable everywhere you look.
“This year we will also be exploring maturation in female athletes. What happens around the growth spurt for males and females is quite different so we need to examine that and see if there's a correlation.”
When I put it to him that arming GAA coaches with all this information could radically change the type of player being produced at county level, Fitzgerald is unequivocal in his response:
“100%.”
Sport
Jack O’Connor’s Kerry squad is looking deeper and stronger (but the proof will be in the eating)
As we reach the midway point of the 2025 season, Adam Moynihan takes a close look at Kerry’s strength in depth
As the Kerry players, management team and backroom staff huddled together for a photo with the Mícheál Ó Muircheartaigh Cup in front of the Hogan Stand, one of the photographers raised his fist in the air, trying to illicit something resembling a celebratory scene. No joy.
Victory over Mayo had been secured in convincing enough fashion but winning the league has never been grounds for buoyant celebrations as far as Kerry are concerned. Retaining Division 1 status and unearthing some new talent is generally enough to tick the springtime box ahead of the serious business of the championship. Once that has been achieved, anything else is gravy.
Going by the disappointing loss to Armagh in last year’s All-Ireland semi-final, the need for new blood was especially great heading into the 2025 season. The team faded badly down the stretch and into extra time against the Orchard County with overdependence on core players glaringly obvious. It wasn’t the only reason they lost but Kerry simply didn’t get enough from their supporting cast on the day.
With that in mind, Jack O’Connor knew he had to work on the depth of his squad during this league campaign, and you’d have to say he made a pretty good fist of it.
Starting in goal, the situation here is clear with Shane Murphy providing back-up to Shane Ryan.
Moving out the field, in recent years Kerry have generally gone with Jason Foley at full back, Tom O’Sullivan at left corner back, and one of Paul Murphy or Graham O’Sullivan at right corner back.
After making his debut in the league in 2024, Damien Bourke has emerged as a genuine right corner back alternative with some strong performances that have vastly enhanced his reputation. Not many Kerry players came out of the Dublin defeat with extra credit to their name but Bourke was brave and tenacious, bursting out of defence and using the ball wisely. He was replaced as a starter by the experienced Murphy in later rounds but the Tralee man capped his league with a goal off the bench against Galway in Salthill.
Dylan Casey also got extended game time in the absence of Tom O’Sullivan and he acquitted himself professionally. He has a solid head on his shoulders and you get the impression that Jack O’Connor would now be comfortable throwing him into any given situation without hesitation.
The versatile Graham O’Sullivan is also an option at corner back and it looks like he’ll need to slot in somewhere other than his natural position of half back as Brian Ó Beaglaoich and Gavin White are nailed on starters at 5 and 7. O’Sullivan lined out at half forward against Galway and Mayo, underlining his flexibility and importance to the team.
There could be a changing of the guard taking place at centre back with Mike Breen seemingly shaking off the injury woes that have held back his progress with Kerry to date. With regular number 6 Tadhg Morley unavailable for selection for most of the league, Breen slotted seamlessly into that crucial central role, and he looked really confident against Mayo on Sunday. As things stand, Morley will be doing well to displace Breen but either way Kerry should have two good centre back options heading into the summer months.
Midfield has been a head scratcher for Kerry for a number of years but in Diarmuid O’Connor and Joe O’Connor they appear to have found a winning combination. Diarmuid was playing the best football of his career up to his injury against Armagh in Round 6 so getting his shoulder right for championship is of paramount importance to Kerry’s chances.
Joe is a guaranteed starter too but his assured display at wing forward against Armagh was interesting in that it opens the door for a third midfielder to start. Seán O’Brien and Barry Dan O’Sullivan both applied themselves admirably when called upon in the league and the manager should feel like he can trust them more now than he did 12 months ago.
Joe O’Connor’s arrival as a half forward candidate has improved Kerry’s options to the extent that it’s difficult to predict how they will line out from 10 to 12 in the Munster Championship. Micheál Burns has done quite well upon his reintroduction to the team after being dropped from the panel in 2024, and Paudie Clifford is looking sharp at centre forward. Tony Brosnan and Dylan Geaney are options along this line too, although Dylan has been operating as a withdrawn inside forward to date – a role Tony is also capable of playing.
Of course, Seánie O’Shea will have to fit in somewhere in this department when he fully recuperates from his knee ligament injury, so it will be interesting to see how Jack O’Connor works this conundrum out. File under ‘good problems’.
Dara Moynihan is still recovering from a hip injury and has not yet featured in 2025. He would naturally be an option at 10 if he can get back up to speed. Meanwhile, Darragh Lyne, Ruairí Murphy and Cathal Ó Beaglaoich all featured at half forward in the league.
David Clifford and Paul Geaney will play at 13 and 14 with Dylan Geaney in pole position to start at 15 on the back of a really good run of form, perhaps excepting the league final in which he was relatively quiet. Tony Brosnan is a prime candidate to challenge Dylan for that spot; the Dr Crokes player has kicked some fantastic scores in each of his last three appearances as a substitute.
As for out-and-out inside forwards, Conor Geaney and Killian Spillane are likely to be used as impact subs.
All told Kerry do appear to have better depth than they had last year, particularly with the emergence of second season players like Bourke, O’Brien and Dylan Geaney as legitimate options, and with Breen beginning to fulfil his potential. Burns’ comeback and Joe O’Connor’s newfound ability to play the 12 position also help.
As always, though, the proof will be in the eating. We will have to wait for the suffocating heat of do-or-die championship matches to find out if this squad is as deep and dependable as it looks on paper.
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