The midfielder has been in fine form despite a persistent niggle, but the problem forced him off before the end of Albion's Boxing Day draw with Manchester City.
Albion boss Roy Hodgson is keeping his fingers crossed the damage isn't too severe but privately he fears that scan results will rule out a key member of his first team for a significant period.
The Baggies boss said: "He's had a groin strain for a while now so we will have to have a look at it. I'm hoping it's not going to be too bad.
"I think it's something that will keep him out for a little while but let's hope it's not too long because he has got himself back in form.
"He's been suffering from a groin injury that we've been nursing him through game to game and it's gone fine.
"His last 10 minutes was 10 minutes too many and if I'd have had some indication he was struggling I'd have taken him off. But unfortunately there was no indication."