With week four of the NFL season wrapped up, teams are looking at the injuries they suffered on the defensive side of the ball. However, not all injuries are created equal in terms of who gets injured and these notable players will be much more difficult to replace.

Markus Golden

The Arizona Cardinals managed to pull out a victory in yesterday's down to the wire overtime victory over the San Francisco 49ers. However, the team also lost one of their young up-and-coming players in outside linebacker Markus Golden. A source told NFL Network's Ian Rapoport that he is out for the season due to a torn ACL, which he suffered in overtime.

He will now be placed on injured reserve and will have surgery in a few weeks. Kareem Martin will replace Golden for the rest of the year.

Paul Worrilow

Following last week's heartbreaking loss to the Atlanta Falcons, the Detriot Lions managed to eek out a road win yesterday over the Minnesota Vikings. On the first defensive snap of the game, the Lions lost linebacker Paul Worrilow to a leg injury. He was helped to the sideline and then carted to the locker room. Worrilow apparently has a sprained MCL and will miss 2-4 weeks, which is a big blow for a Lions team already lacking linebacker depth due to previous injuries.

Veteran Nick Bellore will likely fill his spot unless Jarrad Davis is healthy next week.

Ramon Humber

Following the first quarter ending in the Buffalo Bills' upset victory over the Atlanta Falcons, starting linebacker Ramon Humber went into the locker room.

He underwent further examination and did not return to the game, having a large wrap put on his hand. The Bills announced today that he will need to have surgery on his hand and that he will be out indefinitely. For Humber, this is a bad break as this year was the first time the 30-year-old was a starter. Rookie fifth-round pick Matt Milano will now replace him as the starter.

Cliff Avril and Jeremy Lane

In last night's blowout victory over the Indianapolis Colts, the Seattle Seahawks lost two starters on the defensive side of the ball. Cornerback Jeremy Lane left the game on the first defensive series with a hip injury and did not return. He was replaced by third-round pick Shaquill Griffin. Head coach Pete Carroll said on 710 ESPN Seattle that he has a strained groin.

Defensive end Cliff Avril was also injured in the first quarter while attempting to make a tackle. He walked off under his own power but did not return to the game following a neck injury.

Carroll said that Avril lost control of his hands for a second and that “It'll take us a while to figure this out.”