He is expected to be out of the lineup about three weeks.
"It's the best possible news we could have gotten," said General Manager Ed Wade. "We're relieved. It's the news we had hoped for."
Thome, who hit 47 homers and drove in 131 runs last year, fractured the middle finger of his right hand in a weekend practice session.
Surgery to reset the bone would have sidelined Thome for up to six weeks, a doctor said.