OXNARD, Calif. (AP) -- Dallas Cowboys defensive end Anthony Spencer can't shake a troublesome knee problem.
Backup Tyrone Crawford is out for the season after tearing his left Achilles tendon.The Cowboys have to hope the first two days of training camp aren't a trend after figuring they would be better than last year simply by being healthier. But they're trying not to dwell on it.
''When you let stuff like that creep into you, that's a cancer for the team,'' said Jason Hatcher, one of the healthy defensive linemen. ''Last year we lost a lot of guys, but I think we played our butts off. We're just going to continue to do that.''
The Cowboys couldn't help but feel for Crawford after he went down in a noncontact individual drill during the first full workout of camp Sunday.
Coach Jason Garrett said Monday that Crawford would return to the Dallas area for surgery this week.
Dallas was already without defensive tackle Jay Ratliff, who strained a hamstring on the pre-camp conditioning test after missing 10 games last season with an ankle problem and a sports hernia that required season-ending surgery.
Spencer sustained a hyperextended left knee during offseason workouts and said he ended up with a bone bruise in the same area after the conditioning test. He said he might need surgery and would be sidelined up to three weeks if he did.
''It's concerning to me,'' said Spencer, who is playing on a one-year contract with the franchise tag for the second straight season. ''It's bothering me right now. I really don't know what else to do, so I'm just taking it day by day.''
The Cowboys also are missing Tony Romo's starting guards in Mackenzy Bernadeau, who similar to Ratliff strained a hamstring during the conditioning test, and Nate Livings, who has a foot problem.
It's too early to say the Cowboys are headed for a replay of last season, when six key defensive players had season-ending injuries.
Five of those players - Ratliff is the exception - are healthy and practicing at full speed again, led by linebackers Sean Lee and Bruce Carter.
But the timing of the Crawford injury wasn't good. A third-round pick last year, he figured to be a key backup for a unit that didn't get any help in the draft this year even though a projected top 10 choice was available and Dallas was adding a starter on the defensive line by switching to the 4-3.
If the defensive front was a position of strength, as executive vice president Stephen Jones described it during the draft, at least one player who was a reason for saying that won't play a down in 2013.
''It's a major blow to the defensive line,'' Spencer said of Crawford's injury. ''He was going to be a big part of the defensive line this year. That's pretty much the way last year went, and it's kind of starting off that way right now.''
Kyle Wilber was in Spencer's first-team spot at practice Monday, and Sean Lissemore is filling in for Ratliff. Defensive coordinator Monte Kiffin says there are no immediate plans to start shuffling players, but that could change if the absences of Spencer and Ratliff linger.
History says Spencer will be there when the season starts. He's missed just two games the past four seasons - both last year with a strained pectoral muscle. The Cowboys also expect Bernadeau, Livings and Ronald Leary, one of their backups, to return soon.
''I thought the interior of our offensive line did good (Sunday) - running up and down the sideline,'' Romo said with a smile. ''We've got to get those guys back. Saying that, it's just part of camp. They'll be good to go.''
In the meantime, first-round pick Travis Frederick is finally getting some work at guard after spending all the offseason workouts at center.
Garrett said outside help wasn't coming immediately on the defensive line because the Cowboys have to wait to sign anyone so they can protect Crawford's roster spot. But Dallas will explore the market at some point.
''We have a lot of young guys who we like, guys we want to see more of,'' Garrett said. ''This gives them a chance to show us what they can do.''
The Cowboys ended up with another hamstring injury Monday with tight end James Hanna, but Garrett said he expected the second-year player to be back soon.
''Hamstring injuries have been around for a long time,'' Garrett said. ''That's probably the No. 1 injury that people have. There's a lot of running that goes on in football and sometimes guys get jerked a certain way and they pull their hamstrings.''
