The Arizona Cardinals were a pleasant surprise in 2013, winning 10 games thanks to a punishing defense that ranked first in the NFL against the run.

However, it's been seemingly nothing but bad news for the Arizona defense over the past several months, and the latest blow to strike the Redbirds might be the straw that broke the proverbial camel's back.

On Monday, defensive end Darnell Dockett was carted from the practice field with a knee injury. According to the team's website, an MRI revealed what everyone feared:

It's a huge loss for a defense that just keeps suffering losses.

Granted, the 33-year-old might not be the player he once was. According to Pro Football Focus (subscription required), Dockett ranked a moribund 30th among 3-4 defensive ends in 2013. 

Given his large cap number (nearly $9 million in 2014 and almost $10 million in 2015) and the presence of a pair of talented rookies in Ed Stinson and Kareem Martin, with whom some believe the team's future at defensive end rests, there was quite a bit of speculation that this would be Dockett's final season in the desert.

So the torch gets passed a bit earlier than head coach Bruce Arians and the Cardinals thought. No biggie.

However, it's not just the loss of Dockett, who is one of the longest-tenured and most outspoken players on the team and one of the leaders of the defense.

It's the cumulative effect of yet another starter lost from that stout defense.

Linebacker Karlos Dansby, who led the team in tackles last year, is now in Cleveland. Batterymate Daryl Washington will miss the entire 2014 season thanks to a suspension.

In fact, second-year pro Kevin Minter, who was being counted on to help fill the void left by Dansby and Washington's absence, is out for the rest of the preseason and could ostensibly face season-ending pectoral surgery, according to Mike Jurecki of XTRA Sports 910 radio in Phoenix.

The Cardinals' top inside linebacker right now is 34-year-old Larry Foote, who missed almost the entire 2013 season with a torn muscle in his arm.

Outside linebacker John Abraham, who led the team in sacks last year and who is himself well on the wrong side of 30, only recently reported to camp after seeking treatment for alcohol abuse. Abraham also faces a potential suspension thanks to an offseason DUI.

Safety Tyrann Mathieu's rehab has progressed better than many expected, but the second-year pro still hasn't come off the "physically unable to perform" (PUP) list. He's 50-50 for Week 1 at best.

Dockett's absence leaves one more hole to fill in a division where there's absolutely zero margin for error.

For now, the Cardinals will likely insert ninth-year man Frostee Rucker into the starting lineup. Rucker's a capable veteran who started 16 games for the Cleveland Browns as recently as 2012, but a difference-maker he is not.

Stinson and Martin will all but certainly see more work. It's Stinson who could see the biggest jump, as he would appear a better fit for Dockett's strong-side spot. In fact, back in May, Dockett was talking Stinson up as his eventual replacement:

Well, that timetable's been accelerated and then some, and we're about to find out just how much bending the Arizona defense can do before something breaks.

If it hasn't already.

Gary Davenport is an NFL Analyst at Bleacher Report and a member of the Fantasy Sports Writers Association and the Pro Football Writers of America. You can follow Gary on Twitter @IDPManor.