FORT LAUDERDALE, Fla. (AP) _ Kris Benson will have surgery on his ailing right shoulder, and the Baltimore Orioles right-hander likely will be sidelined for the entire 2007 season.

``At this point, we're probably looking at surgery,'' Orioles executive vice president Mike Flanagan said Thursday morning. ``It hasn't been determined yet with who or when, but it just reached a point with the rehab that it was getting sore and (he) seemed to take a big step backwards.''

Benson had been working out at the Orioles spring training camp, hoping to strengthen his torn rotator cuff through an intense four-week rehabilitation program. Had that process proven successful, Benson might have been able to pitch sometime in 2007.

But Benson, who started the rehab program on the advice of two doctors in hopes of avoiding surgery, left the team Wednesday to return to his home in Atlanta.

The first 10 days of the rehabilitation process were promising, as Benson concentrated on strengthening muscles around the tear. But last week, during daily two-hour sessions with trainer Richie Bancells, Benson began to experience increased pain, and the discomfort did not diminish.

``I don't know if it's just a little bump that I'm going through or what, but the last couple days have been pretty sore. Whenever it gets flared up like it is, it's tough to get that range of motion,'' Benson said at the time.

That setback turned out to be more than Benson could overcome.

``He went through the rehab, he was making progress, things were going well and at one point, he just had this setback,'' Flanagan said.

Benson, who was acquired from the New York Mets in a January 2006 trade for pitchers Jorge Julio and John Maine , was 11-12 with a 4.82 ERA in 30 starts for the Orioles last year, his first in the American League after seven National League seasons with the Mets and Pittsburgh.

He was in the final season of a three-year, US$22.5-million deal, and Baltimore holds a $7.5 million option for 2008 with a $500,000 buyout.

With Benson's status in doubt, the Orioles signed free agent right-hander Steve Trachsel to a one-year, $3.1 million deal in February. Trachsel is expected to take Benson's spot in the rotation.

``You're always disappointed, but we had planned to go along not planning to have Kris for at least half the season, maybe longer,'' Flanagan said. ``So we had made some other plans and had Kris been able to come back, it would have given us additional pitching depth, which we would have welcomed. We've been sort of prepared, I'd say, for Plan B.''

Benson is a career 68-73 pitcher with a 4.34 ERA, but he has had five trips to the disabled list with various arm, elbow and shoulder problems. He had reconstructive surgery on his right elbow in May 2002 and was on the DL from July 26 through Aug. 12 last year with right elbow tendinitis.