David Moyes is keeping his fingers crossed on Andy Johnson's injury after seeing his striker stretchered off in the 2-0 victory at Wigan.
The Everton forward is to have a scan following a collision with Latics goalkeeper Chris Kirkland, and Moyes admits he does not know what to expect.
"He's been taken to hospital. It's somewhere between his ankle and his lower shin but we're not sure," Moyes told Sky Sports.
"When we came off we were a bit more hopeful that there wasn't any damage but obviously we won't know until it's been x-rayed and scanned.
"It would be a massive loss. He's been a terrific player for us but hopefully it's not too serious."
Moyes was pleased with the way his side battled past Wigan in conditions not conducive to good football.
"The pitch was really soft and there was a blustery wind," he explained.
"Wigan made it tough for us today, but we got there in the end.
"We wanted to be dogged and determined, and we wanted to give ourselves a chance by not conceding any goals, in the first half especially."
Moyes also praised Mikel Arteta, who opened the scoring from the penalty spot and sealed Everton's victory with a late second.
"It was a very good penalty kick. He hadn't scored many away from home."
Moyes, whose side are now seventh in the Premiership, added that he was looking to bring in some new recruits before the end of the season.
He said: "I'm hoping to do some business. It's been tough but we've always been looking around and I'm getting a little bit more hopeful that something might happen for me next week.
"We're looking up and trying to catch the teams above us, it would be good to get in that top group if we can."