The growth of women's football has created a worrisome gulf in the sport, with some players stretched by their increasingly packed calendars but many others with too few games, a report by global players' union FIFPRO said.
The study compiled with Football Benchmark showed some players had 60-plus games last season, while others played less than 10, largely due to new or expanded competitions in Europe and North America with little or no development elsewhere.
While FIFPRO's study of 300 players found that Mariona Caldentey played the highest number with 64 games for FC Barcelona and Spain, the average was 33 games, which even with season breaks is significantly less than a game a week.
"There is a two-speed development of women's football," said Dr Alex Culvin, FIFPRO's Director of Policy and Strategic Relations for Women's Football.
"You've got this per centage of players who'll be termed 'higher usage' that are squeezed consistently, both by the construct of the calendar, but also the kind of cadence of the games as well.
"The problems that they encounter are not only the number of games, but the lack of consideration of mandated breaks, so these players are constantly burdened, physically and mentally by the calendar.
"And then underloaded players, because we do know players who are playing less than one game a week, is quite problematic (because they) have an increased susceptibility to injury from detraining and retraining," Culvin told reporters on a video call.
The study "From High-Usage to Underload: A Tale of Two Industries" also found a huge disparity in preparation for the 2024 Paris Olympics.
AS Roma defender Moeka Minami played more than 4 500 minutes of competitive football in the 12 months leading up to the Games, while some of her Japan teammates barely played 1 000.
Spain's Olympic squad had 17 women who had played in at least 30 games before the Olympics, while Colombia had only five.
FIFPRO is advocating for several measures to protect player health and performance including mandatory breaks of four weeks (off-season) and two weeks (in-season), to protect players from overload; and new competitions or the expansion of leagues and other competitions to give underloaded players more games.
Leagues in Germany, Italy, Japan, Sweden and the US have expanded or plan to expand, FIFPRO said, while England's Women's Super League (WSL) last expanded in 2018. Growth remains stagnant and lacking investment, they said, in South America, Africa and Oceania.
The inaugural Fifa Women's Club World Cup will be held in 2026, featuring 16 teams.