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Growth Spurts, Not Talent: Why Some Players Look a Year Ahead

By Joseph Warren · Youth soccer coach and creator of SubGo · September 23, 2026, updated September 27, 2026 · 12 min read

Look down your roster at any age group and you will see it. Two players born five months apart can look like they are playing different sports, one already has an adult sized frame and a long stride, the other still has a kid's body and gets knocked off the ball. Our tryouts and evaluations guide flags this as a scoring risk. This guide goes further into what is actually happening, what real research says about it, and how to coach both players fairly while it sorts itself out.

Who this guide is for

Coaches evaluating, selecting, or building playing time plans for players roughly ages 9 to 15, the stretch where growth timing varies the most. Pair this with our tryouts guide for scoring mechanics and our equal playing time guide for why minutes matter regardless of size.

The short version
  • Two different things get confused. Relative age is which month a player was born in relative to the selection cutoff. Biological maturation is how far along puberty a player is at the same chronological age. Both create real physical gaps that have nothing to do with skill.
  • The gap is bigger than most coaches assume. At the same age, maturity differences alone can mean a 15 centimeter height range and a 15 to 19 kilogram weight range between two players born the same year.
  • Early maturers get picked more, and get more minutes. That part is well documented. Whether late maturers reliably catch up or overtake by 16 to 18, the popular version of this story, is weaker evidence than most coaching content suggests.
  • Real bio banding needs staff and measurement most teams do not have. The underlying idea, though, mixing training groups by physical stage instead of only by age, is something you can borrow informally.
  • Score physical traits and technical traits separately. A smaller player's first touch should not get marked down because he is not winning the ball as often this year.

Two problems, not oneRelative age and biological maturation are not the same thing

Relative age effect is the more famous of the two, and the numbers are stark. A 2025 review in Frontiers in Sports and Active Living covering four decades of data found that "about 40% of elite young adult players were born in the first quarter of the age cohort, compared to just 10% in the last quarter," and that soccer players "born in the Q1 months, were five times more likely to be selected to play International Youth Elite Soccer than players born in Q4." A separate 2025 study of a national youth team selection pool found the pattern just as sharply, 26 of 28 selected U15 players came from the first half of the birth year, none came from the final quarter.

Relative age is about the calendar. Biological maturation is a separate variable layered on top of it, and it is easy to miss because it does not follow a birth certificate at all. Two players born on the same day can be at completely different points in puberty, one already past his adolescent growth spurt, the other a year or two from starting his. Sports scientists measure this against age at peak height velocity, the point of fastest growth during the adolescent spurt, and classify players at a given age as early, average, or late maturers relative to that curve.

The hidden gapHow much difference maturity timing actually creates

This is not a small effect. A widely cited review in the British Journal of Sports Medicine reports that among boys of the same chronological age grouped by maturity status, height at age 11 ranged from about 143 to 156 centimeters and weight ranged from about 36 to 49 kilograms. By age 13, the spread widens further, height from about 156 to 171 centimeters and weight from about 44 to 62 kilograms. That is roughly 15 centimeters and 15 to 19 kilograms of difference among players who are, on paper, the exact same age. None of it reflects a difference in soccer ability. All of it is visible the moment two players line up next to each other.

This is the gap a coach is actually looking at during a tryout, even when the explanation that comes to mind is talent. A study that interviewed academy coaches about their own evaluations found the conflation happening in real time. One coach, describing a bigger player, said "he gets away with a few things because of his size... we were doing 1v1... he was just stepping on the ball," describing size advantage as if it were a technical move.

Over timeWhat actually happens to early and late maturers

The selection bias against late maturers is well documented and not close. In the same 2025 national team selection study, late maturing players "played significantly fewer minutes" than their peers, and among the U15 players selected, roughly 90 percent were early or on time maturers, only about 10 percent were late. A separate study on academy coaches found they were not just picking bigger players more often, they were grading the same performance differently depending on how physically developed a player looked, one coach admitted that an early maturing player with an off game "goes down to a 2," while a late maturing player with the identical performance would get a 4.

Where the evidence gets thinner is the popular follow up claim, that late maturing players systematically catch up or overtake the early maturers by 16 to 18. A 2018 study of professional academy players did find that later maturation was associated with an advantage in self regulation, describing it as "partial support" for what researchers call the underdog hypothesis, and noting that "later maturing players appear to possess a psychological advantage." That is a real, specific, honest finding, but it is about self regulation, not a guarantee of overtaking anyone in ability. There is no well powered study tracking the same players from age 12 through a professional career that confirms late bloomers reliably win out in the end. Treat that part of the story as plausible, not settled, when you talk to a parent about it.

Bio bandingWhat clubs try, and what a small team can actually borrow

Some academies address this with bio banding, grouping players for some training or competition by biological maturity rather than birth year. A 2019 paper in Sports Medicine defines it as grouping athletes "into 'bands' or groups based on characteristic(s) other than" chronological age, while being direct about its limits, "bio-banding reduces, but does not eliminate, maturity-associated variation." A 2026 systematic review of 13 studies covering 861 youth players found real value in short term settings but was honest about the ceiling on that evidence, concluding the current research "relies heavily on short-term match responses and proxy outcomes rather than direct evidence of improved selection accuracy or long-term development." One academy practitioner interviewed about actually running it put the practical reality plainly, "bio banding is maybe more of a luxury tool as opposed to something that sort of needs to happen."

That last quote matters for a rec or travel team. Real bio banding needs staff, cross club scheduling, and physical measurements most volunteer coaches cannot arrange, so do not treat it as a program to build. What you can borrow is the underlying idea, not the method. Rotate small sided game groupings periodically by size and physical stage instead of only by roster age. Build a few sessions around constraints that neutralize a size advantage, two touch limits, no shoulder to shoulder challenges, tight spaces that reward a quick first touch over a long stride, so you can actually see the technical picture underneath the physical one. This is a reasonable extension of the bio banding idea, not a validated program on its own, and it is worth being upfront with yourself about that difference.

PracticeCoaching and evaluating players fairly across the gap

The clearest fix starts on your evaluation sheet. If speed, size, and physical presence sit in the same category as first touch and decision making, a bigger player wins the category by default and a smaller player looks worse than his actual technical level. Split them. Score technical and tactical categories on their own, and treat physical traits as a separate line you weigh deliberately rather than let bleed into everything else, exactly the caution our tryouts guide recommends when building a scoring rubric.

The same discipline applies during the season, not just at tryouts. If a smaller or later developing player is quietly getting fewer minutes because he loses more physical battles right now, that is the exact pattern the research above documents, not a fluke on your team. A deliberate policy of minute equity, tracked rather than assumed, is a direct countermeasure. When you talk to that player's parents, the honest version is not a promise. It is closer to, he is not behind, he has not hit his growth spurt yet, here is specifically what we are doing with his reps in the meantime, and here is how we will know if that is working. That framing is accurate and still genuinely reassuring, without overselling an outcome nobody can guarantee.

Should you measure itFormulas exist, but most teams do not need them

There are legitimate, published formulas for estimating where a player sits on the maturity curve without imaging. One such formula predicts adult height using a player's current height, weight, age, and both parents' heights, and validation studies have found it can land "within 1cm of actual values." The tradeoff is real, it requires accurate parent height data most coaches will not have and may not feel comfortable asking for, and a 2023 review in PLOS ONE cautioned that field methods relying on body measurements alone only show "fair to moderate agreement" with true skeletal age measured through imaging, meaning these are genuinely useful estimates, not diagnoses. The formula is named in the sources below for any coach who wants to look into it directly.

For a volunteer coach running one team, the realistic takeaway is simpler than a formula. You do not need a precise maturity offset number to coach well through this gap, you need the awareness that it exists and is temporary, and a habit of separating what you are watching, physical development or actual skill, every time you evaluate a player. Simply eyeballing who "looks more advanced" has no cited validation behind it at all, so hold that read loosely, it is an observation, not a measurement.

Watch outCommon mistakes

Ask your AI assistant coachDraft the parent conversation, and adjust training across the group

The honest version of this conversation, he has not hit his growth spurt yet, here is specifically what we are doing with his reps in the meantime, is easier to say well when you have already found the words for it once. An AI assistant can help you turn the research above into a short, plain language explanation for a parent whose child looks physically behind teammates the same age, and separately, it can help you think through practice adjustments that account for the maturity gap across your whole roster rather than any one player.

"I coach [age group] [format]. One of my players looks noticeably smaller and less physical than most of his teammates, likely because he has not hit his growth spurt yet. Help me write three or four calm, honest sentences I could say to his parent explaining relative maturity in plain language, without promising he will definitely catch up, plus one or two specific things I am doing to keep his reps and confidence up in the meantime." Paste this before the conversation comes up, not during it
"I coach [age group] [format], and my roster has a wide range of physical maturity this season, some players are already bigger and faster, others have not hit a growth spurt yet. Suggest a few practice adjustments, such as constraints like two touch limits or no shoulder to shoulder challenges, small sided game groupings, or drill variations, that let players at different physical stages compete on more even footing while still developing real technical skill. Do not reference any specific player." Paste this when planning training, not about any one player

Describe a player in general terms only, such as "one of my players" or "a ten year old on my team," and leave out his name and any detail that would let a stranger identify him. The AI can help you find your own words for a general situation, or plan a training session for the group as a whole, not evaluate or make promises about a specific child's future development.

The stat sheet does not care how tall he is

MatchTap tags real events, passes completed, recoveries, shots, to the actual player who made them, so a smaller or later developing kid has a real number to point to, not just how he compares standing next to a bigger teammate. Free, with no account.

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SourcesWhere these ideas come from

A note on this guide's honesty: the relative age effect and the selection bias against late maturing players are two of the most consistently replicated findings in youth sport science, not exaggerations. The claim that late bloomers reliably overtake early maturers by 16 to 18, repeated often in coaching content, is a real and plausible idea with some supporting evidence around self regulation, but it is not a proven guarantee, and this guide has tried to say so plainly rather than pass along a tidier story than the research actually supports.