ALLEN PARK -- The Detroit Lions have not ruled out the possibility they will open the season without rookie linebacker Kyle Van Noy.

The second-rounder did not play Friday night in the exhibition against Jacksonville due to an abdomen injury. He is undergoing further testing this week to determine the nature of the injury and how long it will sideline him.

Van Noy said there's a fear the injury is a sports hernia, which could keep him out for as long as four to six weeks. Detroit opens the season in 16 days against the New York Giants.

"I'm not too sure what the case may be, but that is a concern," Van Noy said. "Any injury is a concern to me. You always want to be healthy, so that'd be pretty concerning."

Coach Jim Caldwell was noncommital when asked whether there's concern this is a long-term injury.

"He still has an evaluation to go through," Caldwell said. "So (the doctors will) make a determination on the length of time and those kinds of things here in the near future."

Van Noy couldn't pinpoint when he originally suffered the injury, but it has worsened over the past few days and finally sidelined him Thursday. The sore spot moves throughout his abdomen, which makes it difficult to understand the issue.

He said he doesn't know if the injury is related to the back pain that caused him to miss some of OTAs.

"It's really frustrating," Van Noy said. "I've never been injured until I got here. That (Jacksonville game) is the first game I've ever missed in my entire life, so it's been pretty frustrating."

Tahir Whitehead got the start at strong-side linebacker, over a healthy Ashlee Palmer and injured Van Noy. He exploded with a team-high 10 tackles and three sacks.

Caldwell said Whitehead has played like one of Detroit's three best linebackers, which means he could be vying for Palmer's job, or even Van Noy's place in the rotation.

And now Van Noy isn't even healthy enough to fight for his position.

Van Noy said he's happy for Whitehead's emergence, and is trying not to think of the politics involved in what's becoming a three-way job battle.

"(Whitehead) played amazing," Van Noy said. "There's little things we all need to work on, but he played lights out. He plays with passion, and that's something we're all going to want to play with. He played amazing, and I hope I can play even close to what he played like.

"It's not my decision (who wins the job). I'm always going to cheer my teammates on. I'm not going to wish any bad things upon anyone. I was happy for him, I'm supportive of him. I'm supportive of every linebacker, no matter if they're in front of me, or behind me. We're a unit, and it takes all of us playing well."

Van Noy said he he is not resigned to the fact he'll be a backup this season, and still intends to fight for a starting job whenever he's healthy enough to retake the field.

"I never want to be resigning. That'd be like giving up," he said. "I'm always going to try to compete to play. That's my job. That's what I'll do when I get back."