Umenyiora, the Giants' two-time Pro Bowl defensive end, today underwent arthroscopic surgery on his troublesome right knee, a procedure that is expected to sideline him for three-four weeks.

The Giants open their regular season in Washington on Sept. 11, which is 23 days away. Their second game is on Monday night, Sept. 19, one month from today.

"It was better to do it now as opposed to midseason," Umenyiora said. "It was going to have to be done, the only question was when. If I'm going to miss a little while, I would prefer it be now than at the crucial part of our season. It's the best decision for the team and myself."

Coach Tom Coughlin was asked if he thinks Umenyiora will miss the opener.

"I don't know about that," Coughlin said before a training camp practice at the Timex Performance Center. "I'm not going to fit anything on the end of that.  Maybe he comes back fast.  Maybe it's three weeks."

Jason Pierre-Paul worked with the first team in today's practice, as he did when Umenyiora was sidelined earlier in camp and in last week's preseason opener in Carolina. The Giants return to action Monday night at home against Chicago.

The procedure on Umenyiora's knee was performed by team physician Russell Warren at the Hospital for Special Surgery in Manhattan.

"It is a simple debridement," said Ronnie Barnes, the team's Vice President of Medical Services, who projected the three-to-four week recovery time.

Umenyiora's knee has bothered him for some time. He did not practice during the first two weeks of training camp. Umenyiora returned to the field on Monday and participated in three practices. After working on Wednesday, Umenyiora decided the best course of action was to have surgery immediately.

"Osi called me at the end of the day yesterday to let me know that he wanted to have the surgery now," General Manager Jerry Reese said. "After practicing for three days he had some swelling in the knee, and it was clear that we were going to have to adjust his practice routine to every other day to maintain his knee. Osi's feeling is he wants to get it cleaned up now because he is looking forward to playing this season, and he wants to (play) without the knee being an issue for him. He told me how much he really enjoyed being back on the field this week, and he's looking forward to getting back out there once he recovers from the procedure."

Coughlin dismissed the suggestion that Umenyiora aggravated his knee problems practicing this week.

"I don't think anything happened…it swelled up," Coughlin said. "He didn't want to continue like this - practice, swell up, practice, swell up. So between the doctors and Osi, the decision was made that they would perform this scope and hopefully eliminate that part of it. Allow the recovery time and then allow him to go back to the field without having this as an issue. Hopefully, it will take less time than the other range, the other extent and we'll get him back as fast as he can."

Umenyiora, entering his ninth NFL season, is coming off a year in which he tied Justin Tuck for the team lead with 11.5 sacks. When he is healthy, the Giants have three outstanding defensive ends in Umenyiora, Tuck and Pierre-Paul. Dave Tollefson will get more playing time in Umenyiora's absence.

Coughlin said Mathias Kiwanuka will continue to play linebacker, as he has since camp began.

"We just keep going, thinking in terms of him being back," Coughlin said. "We'll use different combinations and Tollefson will obviously be involved more with each combination and there will be some packages that we won't be able to use, but probably we wouldn't use them anyway in preseason. Hopefully, these other guys will take full advantage of the playtime and the practice time. We had a couple of issues the other day and some of these young kids got a chance to go. I thought it would be a good idea to play some of these guys extensively anyway."

Late last week, Umenyiora was examined by a specialist in Atlanta who gave him the go-ahead to practice. Despite that, Coughlin said the Giants were not surprised by Umenyiora's decision.

"I don't think that was the case at all," Coughlin said. "As a matter of fact, Ronnie and Dr. Warren talked about a period of time, maybe six to eight weeks ago, when they talked about the possibility of having to have this cleaned out. So I think this is no surprise. There's no surprise."

Umenyiora might have been able to play with the soreness in his knee, but that would not have been an optimal situation for the team or him.

"I think the management part of it would have probably gotten into less field time and some frustration," Coughlin said. "He was very open and very positive with Jerry about getting back on the field, really enjoying the time he was out there with his teammates, really wanting to be a part of our team. So I thought, and I'm hearing it second hand, too, but I thought that those thoughts were very encouraging  and if that's what the situation is, let's get this taken care of today."

Coughlin's expectation is Umenyiora will not be limited when he returns to the field.

"I think that's what he's trying to do," Coughlin said. "They're trying to eliminate the idea that whenever he works and goes hard in practice that the knee swells up.  That's the point, to eliminate that."