IRVING, Texas -- They speak reverently about the Vietnam War vet who has transformed the NFL's worst defense into a squad good enough to help the Dallas Cowboys win 11 games and the NFC East.

And it doesn't matter whether it's an aging veteran such as Jeremy Mincey, a rookie such as DeMarcus Lawrence or a former Pro Bowl player such as Henry Melton describing Cowboys defensive coordinator Rod Marinelli.

Players know when they're in the midst of greatness.

The Cowboys' defense was abject when Marinelli took over for good friend Monte Kiffin in the offseason -- and there was zero reason to think it wouldn't be the worst defense in NFL history by the end of this season.

After all, it ranked 32nd in total defense (415.3 yards per game), 27th in run defense (128.5 yards per game), 30th in pass defense (286.8 yards per game) and 26th in scoring defense (26.0).

Marinelli's one-year remake of the Cowboys' defensive unit plays a large role in the team's dramatic 2014 turnaround. Matthew Emmons/USA TODAY Sports

Times have certainly changed.

In their 42-7 win over the Indianapolis Colts on Sunday, Marinelli's defense held the Colts to a franchise-record 1 yard rushing while limiting quarterback Andrew Luck to 109 yards passing and a 41.7 passer rating.

Indianapolis coach Chuck Pagano removed Luck midway through the third quarter either to protect him from physical harm or to shield his psyche from the butt-kicking the Cowboys' defense delivered.

The Cowboys rank 14th in scoring defense (22.3), ninth in run defense (103.1), 23rd in pass defense (248.1) and 16th in total defense (351.2) this season.

"He's a genius," defensive end Mincey said of Marinelli. "There's a purpose to everything he tells you to do. If he wants you to line up an inch further to the right, then do it. If he tells you to step first with this foot or place your hand there, then just do it.

"He's studied the tape. He sees everything, and he knows that inch is going to help you make a play."

Marinelli has never been a coach who deals well with excuses, so he wasn't interested in hearing about all of the reasons the Cowboys' defense would stink again.

So he didn't really care that Jason Hatcher signed a free-agent deal with the Washington Redskins, DeMarcus Ware was released and linebacker Sean Lee's season ended when he tore a knee ligament during an offseason minicamp.

Sure, he would've loved to have them on the roster, but since they were gone, there was no use whining about it. Instead, Marinelli went about the business of fixing the Cowboys' defense.

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Step one: Simplify a simple scheme even more. Players don't play fast if they don't know what you're doing.

"We don't change a lot of things. We want to allow a man to play," Marinelli said. "I think it's really important to do the ordinary, basic things well -- and the only way is to do those things over and over again.

"Then, you get guys comfortable. Now, you can see their technique and skills and talent come alive. The worst thing a coach can do is confuse a player. Then he's not playing fast."

Then, he continued preaching about unconditional effort. It's not a request; he demands it. No defense plays harder.

This is hardly among the most talented units in the NFL, but it hides a lot of its flaws behind pure effort.

Against the Colts, Lawrence was engaged with the left tackle, rushing the passer at the Indianapolis 38, when he saw Luck complete a short pass to running back Dan Herron.

Lawrence turned, sprinted and made the tackle at the Dallas 22. The Cowboys' defensive linemen make plays like that all of the time.

Marinelli's version of the Tampa 2 defensive scheme is all about the defensive line applying tremendous pressure and affecting the quarterback because he doesn't want to have to blitz to get sacks.

That's why the Cowboys have 10 defensive linemen on the roster and two others on the practice squad. The goal is to create intense competition to be one of the eight players active on game day. Then, they must compete for playing time during the game.