Defensive coordinator Dan Quinn, not a healthy Dak Prescott, is the biggest difference between last season's Dallas Cowboys performance and this year's 2-1 start. 

The turnaround is staggering. 

Yes, Prescott is a legit Comeback Player of the Year candidate and easily a top-10 quarterback. Maybe he even enters the MVP conversation. He shredded the Philadelphia Eagles defense to the tune of an 80.8 completion percentage and three touchdowns during Monday's 41-21 victory. The Cowboys quarterback picked up right where he left off after last year's devastating ankle injury. 

"I think he's clearly playing better now. This is clearly a different football team," head coach Mike McCarthy told reporters after the game. 

But his return signaled what everyone already knew: The Cowboys' offense is already damn good. 

The same couldn't be said of the Dallas D, which ranked among the league's worst, particularly against the run. The unit played soft, undisciplined football under previous play-caller Mike Nolan. How bad was the performance? Through the first six games of 2020, only three teams in NFL history allowed more points. 

Head coach Mike McCarthy made the change within his coaching staff and the results speak for themselves.

"I love doing hard (expletive) with a group of people," Quinn told reporters three weeks ago. "I love being at the game, in the line, right on it. To be here is why I was pumped when Mike offered me the opportunity to come and join him.

"Having that chance and getting a chance to work with the guys here is absolutely where I want to be."

Now, Dallas defenders fly to the football. They're fast, athletic and physical. Quinn's adjustments and schemes are recipes to newfound success, though he's cooking with better ingredients, too. 

Though the Cowboys allowed 367 yards, they mostly shut down the Eagles' offense after their opening drive until the game was basically out of reach. Forcing a pair of interceptions, including a pick-six by Trevon Diggs, fed into the unit's new calling card. Through three games, the Cowboys already snagged six passes from opposing quarterbacks, including Tom Brady and the red-hot Justin Herbert. 

Quinn didn't bring the same old, Legion of Boom-inspired Cover 3 scheme that once helped him become the head coach of the Atlanta Falcons. No, he adapted. 

"I wanted to do as big an after-action on my own self to make sure what I could learn from, things that went well and things that didn't go well," Quinn told David Helman of the team's official website in May. "So, I wanted to kind of do a 360 on the whole process first, the scheme side."

Quinn has the Cowboys attacking after laying the groundwork for the type of talent the team needed throughout the unit to be successful. 

Jerry and Stephen Jones deserve credit for their commitment to the new-look defense. This offseason, the team sunk significant resources into that side of the ball. Free agents Damontae Kazee and Keanu Neal followed Quinn from Atlanta to Dallas. They brought a level of accountability within the system after being starters for the Falcons, though Neal is currently on the Reserve/COVID-19 list. 

During the draft, eight of Dallas' 11 selections, including the initial six, were on the defensive side of the ball. The team seems to have struck gold with this year's 11th overall pick, Micah Parsons. 

Parsons was supposed to take over middle linebacker this season. Instead, he's playing standup defensive end after Demarcus Lawrence suffered a broken foot. Parsons registered half a sack, a tackle for loss, deflected pass and quarterback hit Monday. According to NFL Next Gen Stats, the rookie led his team with five quarterback pressures, three hustle stops and pass-rush get-off. The convert's athleticism is off the charts for an edge-defender, which makes him nearly impossible to handle on a down-by-down basis. 

"He reminded me way early on in my career I spent a lot of time with Michael Bennett," Quinn said last week.

Like Bennett, Parsons is a defensive chess piece who can be moved along the line of scrimmage to take advantage of mismatches, even if he's not playing his natural position. 

All of the Cowboys' recent moves are paying dividends. In other cases, young players are maturing and developing. Cornerback Trevon Diggs is a prime example. Last year's second-round draft pick is turning into a star before everyone's eyes. 

Diggs has an interception in all three games this season. His overall coverage has been exceptional, too. 

"Trying to be around the ball as much as I can," the 24-year-old corner said after his Week 2 performance. "Get my hands on as many balls as I can. Make sure I catch it. You get more interceptions, get turnovers, you lead off on a team, and everybody gets interceptions and turnovers."

Amazingly, Dallas' much-improved defense isn't anywhere near complete.

Lawrence continues to recover from a foot injury and could return later this season. Eventually, Neal will be back in the lineup as well. Second-round rookie cornerback Kelvin Joseph started the year on injured reserve because of a groin injury. Defensive tackle Neville Gallimore is expected back next month after suffering a dislocated elbow. Defensive end Dorance Armstrong, defensive tackle Carlos Watkins and safety Donovan Wilson didn't play Monday because of multiple dings. 

This unit could be even better for the playoff stretch. And, yes, the Cowboys will be in the postseason mix. Who's going to get into their way in the NFC East? Clearly, the Eagles aren't. The Washington Football Team has underachieved. The New York Giants, meanwhile, are one of the league's worst squads. 

Dallas is ready to rumble with the NFC's best and they have the quarterback and defense to finally do so.