Naomi Girma, women's soccer's first million-dollar player, was injured and substituted on her Chelsea debut on Sunday.
The United States defender was taken off after 59 minutes of a 2-2 draw against Brighton and it was not immediately clear how serious the unspecified injury was.
"We'll need to assess her tomorrow, but it doesn't look too bad, but we will see," Chelsea coach Sonia Bompastor said.
The 24-year-old Girma joined Chelsea from the San Diego Wave FC in January for a reported fee of £900,000 ($1.