Stoke defender Marc Muniesa is facing up to six weeks on the sidelines after suffering a torn hamstring.
Former Barcelona defender Muniesa was substituted early in the second half during the 4-1 FA Cup defeat to Blackburn Rovers at the weekend, and Stoke's assistant manager, Mark Bowen, said he will spend at least a month on the sidelines.
"We feared it was a really bad one," Bowen told BBC Radio Stoke. "He had a scan and they've come back saying it's four to six weeks."
He added: "Over the course of the last two months you could argue he's been probably our best defender and showed a lot of maturity.
"He's almost nailed down that left-hand side centre-half spot as his own."
Stoke will also be without centre-back Ryan Shawcross for Saturday's trip to Aston Villa.
"Ryan's had this back problem that he's had in the past and it's reared its ugly head again," Bowen said. "He's gone in yesterday to see a specialist for some more injections.
"We're hoping it hit the right spot and, if so, over the next 48 hours it should progress significantly, but certainly not to put him in the frame for Saturday."