NEW YORK — Johan Santana needs surgery for bone chips in his left elbow and the star pitcher is out for the season, the latest blow to a New York Mets team battered by injuries.

The team said their 30-year-old ace is expected to be ready for spring training next year. The two-time Cy Young winner was examined Tuesday by Mets medical director Dr. David Altchek in New York.

Mets general manager Omar Minaya said Santana was evaluated around the All-Star break, adding the injury worsened in recent weeks, especially after his last start. The GM said "nothing major was there" during the previous checkup.

"It's mostly soreness. It's my understanding from the doctors there are bone chips," Minaya said on a conference call.

"We all want to see Johan Santana pitching in September. But this is a smart move because we want to see him pitching for the long haul," he said.

The Mets had feared a major setback to Santana, who has four seasons left on his $137.5 million, six-year contract. Instead, he will have arthroscopic surgery.

Santana became the 12th Mets player to go on the disabled list, joining David Wright, Carlos Beltran, Jose Reyes, Carlos Delgado, J.J. Putz, John Maine and others.

The development with Santana came on the same day that the fourth-place Mets traded reliever Billy Wagner to Boston for two players to be named. Lefty pitcher Pat Misch and first baseman-outfielder Nick Evans were recalled from Triple-A Buffalo.

What began for the Mets as a season with hopes of reaching the World Series has fallen apart, leaving them out of contention and wondering when the next injury will occur.

On Monday, the Mets said Santana would be scratched from his next scheduled start because of discomfort in his elbow. Strong at the start of the season, his stats had dipped noticeably since June.

"He has not been throwing between starts for quite awhile," manager Jerry Manuel said Monday after the Mets lost 6-2 to Philadelphia. "I would say since before the All-Star break. He has been pitching with this problem, but not with the level of discomfort he has now. Now, it concerns him."

Santana is 13-9 with a 3.13 ERA in 25 starts in his second season with the Mets. He was acquired in a February 2008 trade with Minnesota.

Santana had arthroscopic surgery on torn cartilage in his left knee last October, after the season ended. He went 16-7 and led the majors with a 2.53 ERA in his first year with the Mets.

AP Sports Writer Antonio Gonzalez contributed to this report.