Objective:

To analyze the distribution of Costa Rican professional football players by date of birth, compare them by tournaments and playing positions, and explore the relationship between the relative age effect (RAE) and collective performance and individual participation indicators.

Methods:

A total of 919 male players who participated in 10 tournaments across five years in Costa Rica were grouped into four quartiles, according to their date of birth (Q1= jan-mar, Q2= apr-jun, Q3= jul-sept, and Q4= oct-dec), and six playing positions: goalkeepers, central defenders, full-backs, central midfielders, wide midfielders, and forwards. The collective competitive performance indicator was the team’s position in the table of classification, and individual participation indicators were the percentage of call-ups, matches played, and minutes played.

Results:

It was found a higher percentage of players were born in Q1 and Q2 across nine tournaments compared with Q4 (p< 0.05; OR: 1.46 to 1.70). Among fullbacks, the highest percentage was in Q2, while central and wide midfielders were in Q1. Among the top four teams, there was a higher number of Q1 players; no significant relationship was found between the RAE and the final table of classification (p> 0.05). Players born in Q1 and Q2 had higher percentages of call-ups, matches played during the tournaments, and minutes played per match than Q3 and Q4 (p< 0.03).

Conclusions:

There was RAE in Costa Rican professional football. It was manifested mainly in fullbacks and midfielders. RAE does not influence collective performance, but it affects individual participation indicators.