De La Rosa suffered a partial tear of the ulnar collateral ligament when he threw a 94-mph fastball to Miguel Montero, the fourth batter of the third inning in Sunday's 6-3 loss to Arizona.
The recommendation to operate was made by Dodgers team doctor Neal ElAttrache and arm specialist James Andrews, brought in for a second opinion by De La Rosa's agent, Adam Katz. The Alabama-based Andrews is expected to perform the surgery, but a date has not been set.
De La Rosa said he felt a "sharp pain" on the pitch, but kept pitching with no further discomfort, hitting 99 mph three pitches later in the Montero at-bat and returning to pitch through the fourth inning.
"I don't know how he kept going," said trainer Stan Conte.
"I didn't think it was that bad," De La Rosa said.
But De La Rosa added that "once my body cooled down, it started to hurt." He was told by doctors he will be out from nine months to a year.
De La Rosa conceded he's "a little bit" fearful of the future, but was "accepting reality."
"I've never had surgery of any kind," he said. "I fear a little bit about coming back, but I have to come back. I'm confident I can come back and pitch again."
De La Rosa, who started the season at Double-A Chattanooga, finished with a 4-5 mark and 3.71 ERA for the Dodgers, having made 10 starts and striking out 60 in 60 2/3 innings.
"It's not good and there's not much more to say," said manager Don Mattingly. "You hate to see it happen to anybody. You see all the promise, you hope it's just a setback. It pushes his timetable back. It surprised me. I didn't really think it was this serious, but anytime you hear an elbow, it's serious. I just feel bad for him. I feel bad for us, too."
De La Rosa said he knows more about Tommy John surgery than he should, having been talking about it for five months with his friend, Luis Vasquez, a Dodgers farmhand who missed the 2006 season after the procedure and is looking at a second operation after reinjuring the elbow this year and trying to let it heal without surgery.
"[Vasquez] told me the good and bad of the surgery," De La Rosa said.
The operation -- developed by Dodgers special advisor and former team surgeon Frank Jobe for Dodgers left-hander Tommy John -- involves harvesting an unnecessary tendon from the forearm or calf and, with a figure-eight pattern, weaving it through holes drilled into the ulna and humerous bones to replace the damaged ligament.
The procedure is considered more reliable (an 85 percent success rate by some accounts) than treatments that don't involve surgery, and most pitchers are able to return to the level of performance they attained before the injury.