Cornerback Patrick Peterson (21) and Calais Campbell (93) celebrate the Cards' final fourth-down stop against the 49ers last weekend.

While practicing in the days before playing the Dallas Cowboys three weeks ago, defensive coordinator Ray Horton watched his third-down sub-package unit run a new play the wrong way, and watched the offense score a touchdown.

This was not uncommon, as Horton had worked in new plays during the season. Rather than being upset, Horton stayed matter-of-fact: "Don't worry," he told them. "I'm not going to call that anymore."

Instead of relief, there was pushback from players. Please, they insisted, give us another chance. We won't let you down.

"That was the first time a lot of guys stepped up and said, 'Look we are comfortable,' " safety Rashad Johnson said. " 'We made a mistake, but trust us. We've got your back.' "

The Cardinals' defense has become the backbone of the team during their current hot streak, with three wins in a row and five of six, an unthinkable concept the first month of the season. The learning curve for Horton's defense was painfully steep for a while, and while hasn't been completely negotiated, it has been overcome.

There have been times of clarity. Horton thought it was the week the Cards played the Steelers, and his players could see on video what the defense looked like when executed the way it should be. Coach Ken Whisenhunt thought it was a couple of weeks later, when the defense stood up on a big fourth-down play against the Rams to help snap the six-game losing streak.

But when considering if there had been a singular moment when the switch was flipped for the defense, defensive tackle Darnell Dockett shook his head. "Hell no," Dockett said. "There still ain't been a moment like that."

The Cardinals had to change. Blowing a three-touchdown lead in Baltimore was another letdown in a close loss, after similar endings against the Redskins and Giants. Horton insisted he never once believed the defense wouldn't come together, although he was wondering how long it would take.

Horton understood, though. In Pittsburgh, where the Steelers have mastered the system, "they don't have rookies playing for them." That's because of the learning curve, one that almost every Cardinal faced this season.

To get the players to buy in, he used Steelers' stars as real-life examples. Pro Bowl linebacker James Harrison was cut multiple times by Pittsburgh because he had trouble learning the defense, and even when it started to click he wore a wristband with the plays (like Cardinals linebacker O'Brien Schofield has done).

The story around Steelers Pro Bowl safety Troy Polamalu, Horton said, was former coach Bill Cowher used to worry he was a bust because he was so slow to pick up the system. Polamalu, Horton added, is one of the most "instinctual, knowledgeable players I've ever been around."

"Harrison makes six million dollar a year, and he was cut," Horton said. "I think it gives guys a hope and dream, if you think you are good. Harrison they know as a dominant player, but they don't know the struggles he went through to get there.

"It's the swan on top of the water. It looks graceful, but underneath the water, he's paddling like hell. O.B. (Schofield) was one of those players. Stewart Bradley, Darnell Dockett, Adrian Wilson, they were some of those players who struggled like hell under the water to get to this point. They have a long way to go before they get it. They are just now grasping it."

Early in the season, mistakes were everywhere. Dockett was reminded he was quoted as saying there was a play against Washington in which 10 of the 11 defenders did the wrong thing. Dockett smiled and shook his head. "That's been a bunch of times," he said.

Contrast that to now. Horton said there were two players who didn't execute the right assignment against the 49ers Sunday on Frank Gore's 37-yard touchdown run, which should have covered up once an initial tackle was missed. Earlier this season, mistakes were allowing 80- and 90-yard touchdowns. These days, most of the time, Horton said, a mistake leads to a six-yard gain and "really, no one knows but us."

The full spectrum of the defense can be seen from the Seattle game in Week Three to last week against San Francisco. Before the trip to play the Seahawks, Horton said things had bottomed out enough that he stripped the playbook. That game, Johnson recalled, the defense was so simplified "there were, like, two (play) calls the whole game."

It's much more complicated now. Against the 49ers, cornerback Patrick Peterson got his first NFL sack on a brand-new wrinkle.

And as for that play nearly dumped in practice a few weeks ago? Peterson said it was called "a couple of times" against the San Francisco, and if he recalled correctly, fetched a couple of quarterback pressures.

"Once we fully learn the defense," Dockett said, "it'll be over for a lot of people."