The Dallas Cowboys retained some of the major components of their 2014 version that won the NFC East, but they weren't able to keep DeMarco Murray. While replacing him is simple to some who believe that he was a product of the offensive line, the Cowboys' run game hasn't looked quite the same so far in preseason.

On the defensive side of the ball, Cowboys owner Jerry Jones made a vow to improve his pass rush after watching Aaron Rodgers march up and down the field against him in the Divisional Playoffs round. He added talent via free ageny and the draft, and the defense could make major strides in this area in 2015.

With the regular season set to kick off on Thursday, here are the five most important things we learned from the Cowboys' preseason.

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Joseph Randle might not be the feature back

At the start of training camp, many expected Joseph Randle to take over as the Cowboys' lead back. With the preseason wrapped up, it looks like we're headed for a full blown running back by committee to start the 2015 season. Randle and Darren McFadden have been splitting first team snaps throughout the preseason, and Lance Dunbar has worked in as a change of pace back. It's a small sample size, but McFadden has looked the most impressive so far.

Rookie Randy Gregory can rush the passer

Many viewed rookie defensive end Randy Gregory as one of the ten most talented players in the draft, but off field concerns dropped him to the Cowboys in round two. Gregory racked up the most total pressures and sacks for the Cowboys this preseason. However, he struggled to set the edge and stop the run. Gregory could immediately contribute as a pass rushing specialist in sub packages.

Tony Romo looks better than ever

Tony Romo was limited in practice throughout training camp and the preseason in 2014. With another year in Scott Linehan's offensive scheme, and a full offseason without any limitations, Romo looks sharper than ever. The Cowboys return the same dominant offensive line and every skill position player besides DeMarco Murray. Romo will be asked to shoulder more of the burden early on if the Cowboys can't find the same success in the run game as they did with Murray in 2014.

The cornerback position could become an issue

The loss of Orlando Scandrick to a season-ending injury is a devastating one. Not only is Scandrick the best cornerback the Cowboys have, but he also emerged in 2014 as one of the premier coverage cornerbacks in the NFL. The Cowboys lack depth behind him and the pass defense could be exposed in the early going if the Cowboys' pass rush doesn't improve from what we saw in 2014.

Rookie La'el Collins is the real deal

The Cowboys signed La'el Collins as an undrafted free agent after a tricky off field situation surfaced before the draft, and they may have found the best bargain out there. Collins was a dominant run blocker in 2014 at LSU, and we have seen much of the same this preseason. Collins is still penciled in with the second team, but he could push to start at left guard at some point in 2015.

For more news and analysis on the Cowboys and every team in the NFC East, please head over to the FOX Sports team pages. You can also find Dan on Twitter @DanSchneierNFL.