Striker Mama Sidibe was stretchered off during Stoke City's 6-2 reserve win against local rivals Port Vale.
The 31-year-old, who had earlier scored in the match, required oxygen as he was carried off in the second half with what appeared to be a knee injury.
Assistant manager Dave Kemp told BBC Radio Stoke: "[Physio] Dave Watson is assessing him at the moment.
"It seems to be his knee but we're not sure if it's dislocated or not. It's too early to tell."
Mali international Sidibe has fought back to fitness from ruptured cruciate ligaments and two ruptured Achilles tendons in the past three years.
His injury problems have restricted him to 40 minutes of first-team football since the start of last season.
Sidibe's last appearance for Stoke came in a 2-1 defeat by Tottenham in August 2010, when he suffered his first Achilles injury.
Meanwhile, defender Danny Higginbotham played the full 90 minutes for Stoke, as he continued his comeback from a long-term knee problem.