This latest setback makes it likely Webb is done pitching for the rest of the 2011 season.
"It's disappointing from the standpoint that we knew when we signed him this was a risk-reward deal," general manager Jon Daniels said. "We knew that he had some shoulder history, but thought he was at a point he could push through it and get over the hump and unfortunately, really for no lack of effort or work, it's just not working out."
Webb, 32, signed a one-year deal this offseason for $3 million guaranteed and another $5 million in incentives. The Rangers took a conservative approach in spring training, hoping he would be able to slowly regain the strength in his pitching arm and shoulder and be ready to join the team at some point this season.
But Webb, who had shoulder debridement surgery on Aug. 3, 2009 and hasn't pitched in the majors since Opening Day 2009 for the Diamondbacks, was scratched from his last rehab start for Triple-A Round Rock after he warmed up and felt discomfort in his shoulder.
Webb was attempting to come back, but never found enough velocity or consistent command to be considered ready to return to the majors. On Saturday, before his MRI and visit with Rangers team physician Dr. Keith Meister, Webb was disappointed he couldn't make his last start and was asked if he thought he'd pitch again in the majors.
"I have no idea," Webb said Saturday. "I don't know. It's real discouraging."
Webb won the 2006 NL Cy Young Award and was an All-Star in 2007 and 2008. He won a career-high 22 games before the shoulder got sore enough that he needed the surgery in 2009.
Webb will take some time to contemplate what he will do now and whether he wants to continue to try to make a comeback, though it likely won't be this season.
"I don't think anybody is as disappointed as Brandon is," Daniels said. "He's going to take a little bit of time to digest the information and decide what his next step is. Based on the feedback, it's probably unrealistic to think he's going to pitch this year in the big leagues. Beyond that, it remains to be seen."
Richard Durrett covers the Rangers for ESPNDallas.com.