Phillips was hired as head coach in 2007 because of his expertise as a defensive coordinator.
The Cowboys' defense struggled under Bill Parcells, and owner Jerry Jones wanted someone who could come in and improve the defense.
Phillips did that for the most part during his first three years on the job.
But this year with everything on the line and a Super Bowl berth as the goal, the defense has crumbled, and seemingly so has Phillips' tenure with the Cowboys.
At 1-6, the Cowboys are no longer a playoff contender. They are simply playing out the string over the last nine weeks, which likely will be Phillips' last as a head coach in Dallas.
The Cowboys finished last season with the No. 4 rushing defense and No. 2 scoring defense but have dropped to Nos. 24 and 27, respectively, this year.
The Cowboys have allowed a 100-yard rusher in four of the past five games after going 19 games dating back to 2008 without allowing one.
The problems have seemingly gotten progressively worse each week.
The Cowboys have allowed 76 points and 884 yards in back-to-back blowout losses to the Giants and Jaguars, including 69 points on the last 20 drives in both games combined after the Cowboys took a 20-7 lead against the Giants midway through the second quarter.
Phillips blames himself for not being able to reach his players and teach them fundamentals.
He says it's on him, not the talent on the team.
Linebacker Keith Brooking said coaches coach and players play, and it's the players who are not getting it done.
He played in Phillips' scheme when both were in Atlanta. He said it's a proven scheme and Phillips is a proven defensive coach.
"Look, this game is very simple. It's black and white. You get beat because there is a lack of execution, and we're not executing," Brooking said. "Lack of execution is penalties.
"You call a defense and you have 10 guys who are in their gap, doing what they're supposed to do, and there is one guy who is pressing. He's not getting beat, but things are rolling downhill and he tries to do a little extra and gets out of his gap and that's a lack of execution when it gashes you for 30 yards. There are a lot of different ways you aren't executing."
Still, scheme has been a problem. Opponents have taking advantage of mismatches and have caught the Cowboys in blitzes or bad defensive calls for big plays.
What's also true is several players aren't playing well and others aren't playing up to expectations.
Alan Ball has been poor at safety in place of the departed Ken Hamlin.
He's simply not been around the ball enough or at all.
Two other players who have been noticeable for their poor play or lack of playmaking are cornerback Mike Jenkins and linebacker Anthony Spencer.
Jenkins was a Pro Bowler last season and was widely considered the team's best cornerback. He has been targeted by opposing teams for big plays all season. He also leads the league in pass-interference penalties.
Spencer was the team's best defensive player at the end of last season with eight sacks in the final eight games. He has just three so far this year and has failed to make a consistent impact.
"It's a regression with our team overall," Phillips said. "If I knew why each player wasn't playing up to the level he was playing before. Part of it is we are not playing fundamentally sound. We are not playing as well as we want to play."
SERIES HISTORY: 24th regular-season meeting. Cowboys lead series, 12-11. Dallas has won three of the last five meetings. Green Bay won last season, 17-7.
The end of Wade?
CowboysHQ Top Stories
Cowboys Youth Key in 31-17 Win over BearsThe Cowboys took care of the Bears 31-17 to finish September 2-1 and drop the Bears to 0-3.
CowboysHQYesterday at 8:58 PM
Cowboys T. McClain + His Pal - His Big ToeARLINGTON - In preparation for tonight's Bears at Cowboys game, I go 1-in-1 with maybe Dallas' best player on D, Terrell McClain - and his new best friend, his so-far-cooperative…
CowboysHQYesterday at 6:34 AM
Cowboys 1st and 10: The Front Four ShuffleEach weekend I provide 10 quick hits on the Cowboys. Marinelli is turning to his tackles to create an edge rush, the debate about Romo’s job security is a little insulting, and…
CowboysHQSaturday at 1:00 PM
Dallas Cowboys Fantasy Picks for Week 3Here are CowboysHQ.com's Dallas Cowboys Fantasy Football picks for Week 3 against the Chicago Bears (plus a Norm Hitzges special!)
CowboysHQFriday at 10:00 AM
Cowboys STARCast: 'Alpha Pup' Vs. The BearsCowboys STARCast: 'Alpha Pup' + 'Butterfly' + Big Changes On D Vs. The Bears - Hear from Tyrone, Jack, Church and Durant!
CowboysHQFriday at 7:05 AM