Port Vale boss Micky Adams revealed substitute Ashley Vincent suffered a suspected broken leg during the closing stages of the 2-0 defeat at Bristol Rovers.
Vincent was hurt as he tried to latch onto an 80th minute rebound when Lee Hughes' shot was brilliantly saved by Steve Mildenhall.
There did not appear any contact with an opponent, but Vincent was stretchered off and afterwards Adams said: "It looks like a fractured tibia. We're not sure how Ashley did it and we won't be certain of the damage until we get him checked out, but it doesn't look good.
"I'm concerned about our form because there is a lack of confidence among the players and they are not looking the same as earlier in the season. We lost two goals to poor marking at set-pieces, which is always disappointing. But I felt we created the best chances and failed to take them.
Ryan Brunt netted with a downward header after seven minutes and a low near post shot in the 38th minute as Vale failed to defend two Oliver Norburn corners from the right,
Rovers' victory moved them into mid-table and continued the remarkable revival since John Ward was appointed as manager in December.
He said: "We had 11 players unavailable, which is half of my squad, so I couldn't be happier with the performance and result. I asked players like Danny Woodards and Jim Paterson to do a job for me in unfamiliar positions and both reacted positively and made big contributions.
"The whole squad have been magnificent since I took charge. The job of retaining Football League status is not quite done yet, but we are progressing all the time. We lost Oliver Norburn in the second half so our injury list has got even longer. His ankle is very swollen and it looks as though he will miss games.
"I keep challenging the players to go one step further and the keep meeting the challenges. I wanted to see how we responded to a poor display at Chesterfield on Saturday and got just the response I wanted."