Mears spent two months on the sidelines with a bicep problem earlier on this season, meaning extra care will be taken to ensure he is fully fit before returning to action.
The 31-year-old is having a scan to assess the damage today but he looks like being out of the equation for Saturday's Twickenham encounter with the current table toppers.
"Lee Mears has got a bit of a bicep hematoma, as they have described it," said interim England boss Stuart Lancaster.
"He has gone for a scan today so we will wait and see what happens. He has had two bicep injuries before so we want to be careful.
"Lee is still at Bath. We have brought Chris Brooker in from Quins. He arrived this morning and will stay with us until tomorrow afternoon."
Mears hasn't featured for England so far in the 6 Nations, with Lancaster handing Northampton's Dylan Hartley the starting shirt and promoting Wasps' Bath-bound Rob Webber to the replacements' bench, but his potential absence is still a blow as Webber has just a single cap to his name and Brooker is yet to feature for the senior side.
And Mears isn't the only fringe player to suffer a setback today as Charlie Sharples also looks like being unavailable for England selection.
The Gloucester wing, who, like Mears, wasn't required in the matchday 22 against Scotland or Italy, has a dead leg and is expected to return to his club rather than press his claim for an international berth later on this week.
"Charlie has picked up a dead leg so he won't be training," added Lancaster.
"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."