"We got bad news on Wilson," Giants manager Bruce Bochy had said Saturday. "He took an MRI, and it shows structural damage with his elbow."
Bochy said it was "likely" Wilson was headed for Tommy John surgery, which would be the second of his career. He also underwent the same procedure when he pitched for Louisiana State University in 2003.
Wilson reported some discomfort with his elbow to Giants head athletic trainer Dave Groeschner on Friday, which led to the testing.
"You're always hopeful to see something else," said Bochy of plans to have Wilson examined by team doctor Kenneth Akizuki and Dr. James Andrews. "We're going to get a second opinion and even a third opinion."
Wilson pitched Wednesday and Thursday in Colorado, struggling to save the Giants' 4-2 win on Thursday. He needed 32 pitches to finish the ninth, allowing one run on three hits and walking a batter. His loss of velocity was not a major concern at the time.
"You feel for Willie," Bochy said. "He worked hard on his rehab, Spring Training went well and there were no setbacks. It looked like he was all ready to go, and then this happens."
Wilson, one of the heroes of the 2010 World Series championship run, was not immediately made available for comment.
Meanwhile Bochy said he will return to the closer-by-committee setup that he used last year when Wilson was out.
"We'll figure a way to get this done," Bochy said. "We do have guys who are comfortable pitching late in the game."
Wilson has recorded 171 saves since joining the Giants in 2006. He saved a career-best 48 during San Francisco's title run. He had a 1.81 ERA in 2010, but fell off to 3.11 last year, when he saved 36 games after starting the year on the disabled list with an oblique injury.
During Spring Training, Wilson admitted he pitched with a sore throwing elbow and a bad hip through much of last season, spending more than a month late in the season on the DL with inflammation in the elbow. He also declared himself healthy this year.
"Once I get out there, game-ready, throwing to hitters, it's not going to be a surprise when I do well," he said in February.
Groeschner said the Giants took immediate action when Wilson informed them of his troubling elbow.
"He's stiff and not moving great," Groeschner said. "Other than that, there's no outward signs. I know it's the weekend, but we'll make some calls and contact doctors across the country."
Wilson allowed a run in each of his two appearances so far this season.
Rick Eymer is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.