Yankees reliever Joba Chamberlain during warmups prior to facing the...

Yankees reliever Joba Chamberlain during warmups prior to facing the Blue Jays at Yankee Stadium. (May 24, 2011) Credit: Jim McIsaac

Yankees reliever Joba Chamberlain characterized Wednesday's assignment to the disabled list as a form of risk management. "Not serious," Chamberlain insisted. Merely a nagging stiffness on the inside of his pitching forearm to be rested.

"Just one of those things where you say, 'Let's see what it is and stop worrying about it,' " Chamberlain said. "There's no pain. I can do whatever I want. It's just that, when I'm done throwing, it gets tight.

"That was the biggest thing for me. I mean, I'm a hypochondriac when it comes to being hurt because, knock on wood, I'm not hurt very often. So just trying to take the doubt out of my mind of what's going on, I decided to say something."

Chamberlain informed manager Joe Girardi of his discomfort on Tuesday and Wednesday underwent an MRI that revealed a strained flexor muscle, just below and inside the elbow.

Chamberlain said he couldn't pinpoint when he first was aware of the tightness, and his efficiency has been such -- a 2-0 record with a 2.83 ERA in a team-high 27 appearances -- that Girardi would not second-guess having Chamberlain throw 35 pitches in Sunday's victory in Anaheim.

"It's really pretty amazing," Girardi said. "He probably pitched with it for a while. He had been getting treatment on his elbow for a couple of weeks, which is really not abnormal for a pitcher to ice after games and at times to be a little bit stiff. But his stuff had been really good and he had pitched really well, which didn't lead us to believe that he really had an issue."

Lifting weights and other non-baseball activity is no problem, Chamberlain said, expecting that not throwing for "10 to 14 days" will solve the problem. But having his health fraught with ambiguity is not helpful to the Yankees' bullpen, which has leaned on Chamberlain and David Robertson since Rafael Soriano went on the disabled list on May 17.

In Soriano's absence, Chamberlain didn't allow a run in his last eight appearances. Girardi said that Robertson, who hasn't given up a run in his last 10 outings, will become the eighth-inning reliever, with Luis Ayala and Boone Logan filling Robertson's role as bridge to the setup man.

Chamberlain, wearing a white sleeve on his right elbow, repeatedly contended that, "If you asked me to pitch today, I'd pitch today." He won't be asked.

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