EAST RUTHERFORD, N.J. — Second-year player Dave Tollefson said his first thought was for his teammate.

"I just hope he's alright," Tollefson said after watching starting defensive end Osi Umenyiora helped off the field and onto a cart with a left knee injury. "Our d-line, we have a pretty close bond. We're like a band of brothers. So first thing is I want Osi to be OK."

And his next thought?

"The second thing that was on my mind was: It's time to go, Dave!" he said.

Tollefson replaced Umenyiora with the starting defensive unit in Saturday night's 10-7 loss to the Jets. If Umenyiora is unable to play in the regular season opener on Sept. 4, it likely will be Tollefson who replaces him. And while most Giants players have said they are confident in the depth the team has at the position and their ability to play without the man who led the team in sacks the last four years and the only Pro Bowler from the Super Bowl season, not everyone was willing to move on just yet.

"You're saying lost like he's gone, but I don't think he's gone anywhere," linebacker Antonio Pierce said when asked about the Giants' ability to play well last year after losing players to season-ending injuries. "The game is in 11 days after today. We have 11 days to get better, 11 days to get healthy. Hopefully he can get healthy in 11 days."

It certainly didn't look that way to the observing eye when Umenyiora, his head buried in his hands, received some words and a pat on the shoulder from defensive line coach Mike Waufle while being driven off the field. On a third-and-7 play from midfield early in the second quarter, Umenyiora made a move upfield against Jets tackle D'Brickashaw Ferguson and appeared to have his left foot snare in the artificial surface at Giants Stadium. He said his knee locked up on him.

"It just seemed like he turned the corner and kind of took an awkward step," defensive tackle Barry Cofield said. "The turf is hard and playing at the speed and trying to turn that edge, it's easy to tweak something."

"I really don't know what happened," Ferguson said. "I'm just not sure."

Umenyiora fell to the ground and got up to continue his pursuit of the quarterback. He was pushed by Ferguson and began limping severely before crumbling to the surface once again. He had to be helped to the sideline, unable to put any weight on his left leg, and sat on the bench for several minutes before being driven through the tunnel.

X-rays were negative and coach Tom Coughlin said he was told by doctors that there was no ligament damage. Umenyiora, who left the stadium on crutches before his teammates came off the field, will undergo an MRI on Sunday.

If Umenyiora is unable to play for an extended period of time, the Giants might consider moving linebacker Mathias Kiwanuka back to his natural position at defensive end. Besides Tollefson, they also have veteran Renaldo Wynn. If they lose Umenyiora, they would be without the two bookends of the defensive line that helped them to a championship. Michael Strahan, the other bookend, has retired.

"We know we have the personnel to step up in his absence," Kiwanuka said. "Obviously he's a Pro Bowler, you can't replace someone like that without feeling it at least a little bit, but we understand we do have enough people here to get the job done."

Tollefson said when he came onto the field Saturday night, no one in the huddle gave him any special encouraging words. It was business as usual.

"That's the great thing about this team is I feel like they have some faith in me," Tollefson said. "Those guys, I go out there and it's just like I'm in, let's go. Osi, he missed a couple of practices during training camp, so they're comfortable with me.

"I'm just one less," he said, pointing to his jersey number. "I'm a 71 instead of a 72."

If Kiwanuka is forced back to his natural position at defensive end, that would leave the Giants with a gap at strong side linebacker, but assuming Pierce is healthy enough to start the season, Blackburn could play there.

When Kiwanuka missed a practice this past week, impressive rookie Bryan Kehl took his spot with the first unit.