Leading up to the heavyweight fight against Pittsburgh, Let's Talk Numbers will be presented in two parts this week. Part II will be up Friday morning.

In this week's first installment of Let's Talk Numbers, we determine if the Dallas Cowboys' defense has improved after the debacle in St. Louis. Since Wade Phillips took a more "active" role in the defensive playcalling against Tampa Bay, the Cowboys are 4-1 and the defense has started to show signs of just how good they could be.

Are things as good as they seem, or is the defense performing at the same level as they were to start the season? Follow the jump to find out.

The Dallas Cowboys' defense is an enigma.

Since having the league's number one defense in 2003, the Cowboys have ranked 16th, 10th, 13th and 9th in the years since. When Bill Parcells was hired as head coach he immediately started to mold the defense into his version of the 3-4 defense, and the transition has not gone as smoothly as hoped. Teams that run successful 3-4 defenses (such as Pittsburgh) have had years to build around the scheme and determine personnel decisions to best fit their goals. The Cowboys are on just their fifth season as a 3-4 defense and despite having some of the top defensive players in the league, have consistently underperformed.

When Wade Phillips was hired prior to the 2007 season, a big part of his allure was his track record with the 3-4 defense. His defenses in San Diego were some the most aggressive in the league, helping propel the Chargers to a 14-2 record in 2006. As coach of the Cowboys, it was hoped that he would be able to fix an ailing 3-4 defense that had been a disappointment the past few seasons. He promised a more aggressive, "one-gap" style of defense that would better utilize the playmakers on the team. More importantly, his defenses would cut down on the big plays that plagued the Cowboys' defenses of the past.

For the most part, the changes in 2007 worked. After a transitional period to start the season, the Cowboys defense allowed less big plays and half as many 40+ yard pass plays as they did in 2006. The Cowboys also raised their sack total from 34 to 46. Yet things still weren't as good as hoped, with the Cowboys finishing with the 9th ranked defense in the league. Most concerning was how the Cowboys were susceptible to quick scoring drives with big chunks of yards allowed in the passing game at a time.

In 2008 came more promises of an improved pass defense, with the Cowboys drafting two ranked cornerbacks in Mike Jenkins and Orlando Scandrick and trading for Adam Jones. The Cowboys also added All-Pro linebacker Zach Thomas and nose tackle Jay Ratliff was poised to anchor a dominant defense.

Unfortunately things didn't go as planned. Injuries to key players were a major factor, but at times the defense seemed to play without emotion or intensity. A Cowboys defense built on aggressiveness had lost it's punch. The whole thing threatened to fall completely apart following a 34-14 loss to St. Louis. Players were frustrated with the schemes and playcalling of defensive coordinator Brian Stewart, and something needed to be done to avoid complete disaster.

Following the loss to the Rams Wade Phillips announced he would be taking a more personal involvement in the defense, in particular the playcalling throughout the game. That week the Cowboys beat the Tampa Bay Buccaneers 13-9 on the back of the Cowboys best defensive effort in years. Since Wade Phillips stepped in, the team is 4-1 and playing with a newfound level of intensity and emotion. But how much have things changed? Let's take a look at the defensive numbers before and after Wade's intervention:

At first glance the numbers seem fairly similar, but with a closer look there are several small differences that really stand out and show just how different the Cowboys defense has been playing lately.

Pass defense: I decided to use net yards passing and average yards allowed per dropback to truly gauge the newly aggressive defense and how it has improved the pass defense. Despite teams throwing five more times per game, the Cowboys are allowing less yards passing and nearly a full yard less per pass play. They are also averaging four sacks per game and while the number itself is not much higher than it was, the difference is in who is getting the sacks. Bradie James has four sacks in the past five games, while having just 5.5 sacks in his career prior to 2008.

James hasn't been blitzing more since Wade stepped in, but the type of blitzes he's been involved in has changed as well as when he blitzes. This has allowed him to come free to the quarterback more often than in the past, and with the offense already accounting for DeMarcus Ware and company, James has made the most of his opportunity.

The chief complaint earlier in the season was how far off receivers the Cowboys' cornerbacks were playing, as well as the amount of zone coverage the defense was running. This was allowing teams to consistently find holes in the zone,and while the Cowboys weren't giving up big plays, offenses were gashing the Cowboys with intermediate and short routes.

After Wade Phillips' intervention the Cowboys started playing more press coverage, especially after Terence Newman returned from injury. This was a direct result of the Cowboys' pass rush stepping up, allowing the coaches to have more faith in the secondary. This combined to give the team a newfound self-confidence, and it showed on the field.

Turnovers and red zone efficiency. The most alarming part of the Cowboys' defensive play to start the season was the lack of turnovers, most notably interceptions. Since Wade Phillips aggressive defense stepped up, the Cowboys have nearly doubled the amount of turnovers forced per game. The team still only has one defensive touchdown this season, but if the cowboys continue to force two turnovers a game then the path to the playoffs will be just a bit easier.

The biggest change has been in the Cowboys play in the red zone. Despite a 5/5 debacle against the Giants, the Cowboys have improved their red zone efficiency by 12%. Goal line stands have come at the most important times as well, not allowing the team to get behind early when things could have gotten out of hand in a hurry.

Bottom line: The final numbers aren't perfect and are affected by factors outside the defense. When Romo was out the offense consistently put the defense in a bad position. With the return of the star quarterback the entire team was infused with a newfound energy and emotion, not just the offense. It's tough to tell just how much Wade Phillips' influence has changed the play of the defense or if the return of Romo sparked the play.

Here are the numbers that matter most. Before the Tampa Bay game the Cowboys defense was allowing 22 points per game. Since then the defense has given up 17 a game, a five point swing. That is what is most significant and the only numbers that count. Whatever Wade Phillips has done, no matter how much or how little, he needs to continue doing it.