"That's great because we thought it would be longer," manager Ron Washington said Monday. "It looks like we'll have a chance to get him back after the [July] All-Star break. At least it won't be September."
The team had feared that the injury was a hernia similar to the one that shut down second baseman Ian Kinsler for 12 weeks last year.
An MRI exam on Monday confirmed the diagnosis of the partial tear.
Dr. William Meyers, who examined Hamilton in Philadelphia, will perform the surgery.
Hamilton was injured May 17 when he crashed into an outfield wall while making a leaping catch against the Los Angeles Angels. He went on the disabled list last week.
Also Monday, the Rangers said starting pitcher Brandon McCarthy has been diagnosed with a stress fracture in his right shoulder blade and will miss Tuesday's scheduled start against the Toronto Blue Jays. The right-hander was out nearly four weeks because of a similar injury in 2007. McCarthy is tied for his career high and the team lead with five wins.
The Rangers said Doug Mathis would make Tuesday's start, unless he was needed to pitch in relief Monday. The 26-year-old right-hander has pitched only one inning for Texas since being promoted from Triple-A Oklahoma City, where he was 4-2 with a 2.89 ERA in 10 starts.