Crewe Alexandra manager Steve Davis fears Neil Etheridge's thigh injury will signal the end of the Fulham goalkeeper's loan spell.
The 23-year-old had scans after hurting himself with the final kick in Saturday's 1-0 win against Crawley.
Etheridge joined the Alex on loan until 1 January last month.
"The worst scenario is three to five weeks out which virtually ends his loan. If he is out, it will be a big loss," Davis told BBC Radio Stoke.
The clean sheet against Crawley was Crewe's first in seven games in all competitions.
Before the London-born Phillippines international's arrival at the Alexandra Stadium, the League One strugglers had conceded 36 goals in 16 league games.
Having failed to settle on a first-choice keeper, swapping between veteran Steve Phillips, Alan Martin and Ben Garratt for the first 21 games of the campaign, Davis was quick to install Etheridge as his number one.
"He has been brilliant for us in the three games [he's played], getting better and better," Davis said.
"He has made some brilliant saves, has been a real presence in goal and been a terrific lad to work with."
Davis added Ryan Colclough, who has struggled with a chest infection, and Mathias Pogba, sidelined with a knee injury, will both benefit from the 14-day break before their next League One match at Coventry because they are no longer involved in the FA Cup.
"Ryan is back training fine and Pogs has joined in some running," Davis said.
"In two weeks time we could be in a much better position, certainly with Ryan back and Pogs being in the squad."