Somerset captain Marcus Trescothick could be out for a further two or three weeks with an ongoing ankle injury.
But the surgery revealed he had ruptured a tendon and director of cricket Brian Rose says he could now be sidelined for at least two months.
"It's more serious than we first thought," Rose told BBC Radio Bristol.
"Realistically we are talking around eight to 10 weeks (in total)."
Meanwhile, Rose admitted the county were interested in signing Ajmal Shahzad, who was released by Yorkshire on Thursday.
"It's a possibility," he said. "He's one of several we've had a look at.
"There are several counties chasing him and we've registered an interest but I think it could take three or four days to sort out."
The England international appeared in Yorkshire's first three County Championship matches this season but is not involved in the current match with Leicestershire.
The Tykes say they mutually agreed to release the bowler because he was "unhappy" at Headingley.
The 26-year-old has taken 135 wickets in his 49 first-class appearances, including one Test against Bangladesh in 2010, and scored 1,189 runs.