OXNARD, Calif. -- Dallas Cowboys offensive coordinator Scott Linehan said Sunday he's been really impressed with rookie Dak Prescott and Jameill Showers as the two compete for the backup quarterback spot.

And that's coming from the man who was Kellen Moore's biggest supporter.

Moore is out the next three to four months after undergoing surgery last week in Dallas to repair his fractured right ankle. The Cowboys, meanwhile, remain patient on the backup quarterback front -- not aggressively pursuing a veteran -- as they give Prescott and Showers more time in practices.

Linehan liked what he saw Sunday in practice from Prescott and Showers. Prescott's work came during team and 7-on-7 drills. Showers handled all 16 plays of the annual Blue-White Scrimmage on Sunday.

"They did some really good things. There is that occasional, 'You got to get the ball out here.' But I didn't see mental errors," Linehan said. "Some of the stuff was the process and the mechanics of the play, but knowing where they're supposed to go and their reads and pulling the trigger on the play, you can really see [that]. They're not just guys who are out there running around because they can run and they're athletic. These guys work well in the pocket. They both can really throw it and they have that double-threat thing. We haven't really seen them play games where they can make it happen with their feet, but they start by looking for the throw first and if the defense is going to give them the ability to run that's going to be another part of their game."

You won't likely see how much of a weapon Prescott can be when he escapes the pocket until he plays in a preseason game. Tony Romo isn't expected to play Saturday in the Cowboys' first preseason game against the Los Angeles Rams. Expect Prescott to play the first half with Showers taking most of the second half.

Prescott didn't take a snap under center until he participated in the Senior Bowl in January. Linehan said he's improved with each practice under center.

"Very rarely do I sit there and think he's got to get out of there or he's slow getting away from the center or he's clumsy on the tempo of his drop," Linehan said. "He worked his tail off, as did Jameill, in the offseason program."

Showers has been slightly better than Prescott throughout training camp, but Prescott is still working with the second-team ahead of the second-year player.

"Jameill has a really good arm. He throws a real classic ball," Linehan said. "He's processing things as guys that get more experience do better, so the ball is coming out quicker. As he's gone through camp, his accuracy has been really good."