Exeter's faces a nervous wait to see if he will be fit for the start of the season after suffering an elbow injury.
Lewis has undergone a scan after being hurt in last week.
The 25-year-old is set to miss the Chiefs' remaining warm-up fixtures against Ulster and Worcester.
"The initial prognosis is there is no fracture, so it's going to be a bit of a wait and see," said boss Rob Baxter.
"He had an MRI scan on Monday night and we're obviously hoping it won't show too much ligament damage.
"If that's the case, it will just be a case of getting him rehabbed, re-strengthening the joint and see how we go.
"He's certainly not going to feature this weekend against Ulster and he's unlikely to feature against Worcester. We'll just have to monitor him after the Worcester game on a week-by-week basis."
Lewis made 24 starts last season, establishing himself as the club's first-choice number nine ahead of Haydn Thomas after a