Jess Fishlock is a major doubt for Wales' prestigious friendly against world champions USA on Sunday.
Wales had hoped the midfielder could feature for OL Reign on Friday in the National Women's Soccer League (NWSL) and still play a part against the US.
But she was forced off early in Reign's 1-0 loss to Orlando Pride.
Fishlock, 36, went down off the ball in the 23rd minute and received treatment for several minutes before being replaced by Nikki Stanton.
Gemma Grainger's Wales side are already without suspended captain Sophie Ingle for Sunday's match in San Jose, and forward Rachel Rowe will miss out because of a calf problem.
Wales now face the prospect of being without Fishlock - her country's most-capped player, with scored 36 goals in 141 international appearances.
It would also be a personal setback for Fishlock, who has played in the US since 2013 but is yet to face their national side.