West Ham United manager David Moyes is concerned about the injury Manuel Lanzini picked up in Saturday's 1-1 draw against Bournemouth.
Lanzini had to be replaced by former Manchester United striker Javier Hernandez, who grabbed the Hammers' equaliser.
"Lanzini is a worry," Moyes admitted. "It looks like a hamstring but we'll get it scanned on Sunday.
"I think the Lanzini thing has come more from fatigue. He's very important [to us]. I think he was talked a lot about when I came and, I have to be honest, I didn't see that in the first half-dozen games or so.
"I think in recent weeks we are beginning to see what everyone was telling me and he is starting to form a great understanding with Marko [Arnautovic] although we didn't quite get the magic we needed in front of goal."
Hernandez scored West Ham's equaliser immediately after Ryan Fraser had given the Cherries the lead and Moyes is keen to keep the Mexican forward.
"There's speculation about 'Chicharito'," he added. "But there's been speculation about Andy Carroll, Diafra Sakho… about every man and their dog here really."
West Ham, 13/8 to finish in the top half of the Premier League this term, can be backed at 50/1 to win the FA Cup.