The Bath forward has not been able to make either of Stuart Lancaster's opening two matchday squads in the competition so far, and may be absent from this weekend's game at Twickenham against the unbeaten Welsh.
Harlequins' Chris Brooker has been called up as cover, Lancaster revealed this afternoon.
"Lee Mears has got a bit of a bicep hematoma, as they have described, it at the moment," England's interim head coach said.
"He has gone for a scan today so we will wait and see what happens. "He has two bicep injuries before so we want to be careful.
"He is still at Bath. We have brought Chris Brooker in from Quins. "He arrived this morning and will stay with us until tomorrow afternoon."
Gloucester winger Charlie Sharples, who is also yet to feature in the Six Nations, is another doubt for Saturday's game after suffering a dead leg in training.
"Charlie has picked up a dead leg so he won't be training. He has stayed with us. He will probably head home tonight. He won't be fit to train tomorrow, but I am sure he will be fine for Gloucester at the weekend," Lancaster added.
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