OXNARD, Calif. -- For Dallas Cowboys quarterback Dak Prescott, Saturday's preseason opener against the San Francisco 49ers means little.

He might play and he might not. He took only 10 snaps in the first preseason game in 2018 against the Niners. Maybe you remember the 30-yard touchdown pass to Michael Gallup. Maybe you don't.

But for Cooper Rush and Mike White, who are battling to be Prescott's backup, Saturday's game (9 p.m. ET, NFL Network) means a lot.

"That's their season," quarterbacks coach Jon Kitna said. "I never understood the backup quarterback that went in and played slow and used the whole play clock and that stuff. I was trying to get as many plays as possible. Let's go faster, faster, faster, faster, faster. The linemen didn't like you for a minute, but then they ended up liking you because the other guys got tired. I think it's important to get as many quality reps as you can in the preseason because those are real and it's hard to get real reps in this league. It's going to be really important for them and their development. And their competition."

The Cowboys' 53-man roster, although relatively young, is largely set. None of the starting and key contributor positions seem up for grabs.

Backup quarterback is different.

Ask people throughout the Cowboys organization if the backup to Prescott for the Sept. 8 regular-season opener against the New York Giants is on the roster, and you get mostly the same answer: Maybe.

If Rush or White can perform well this preseason, then they can answer one of the only looming questions out of training camp. If they don't, then you have to wonder if the Cowboys would enter a season with such high expectations with such great inexperience at the game's most important position.

"You just want to see how they handle themselves, really at every position but particularly that position. Meetings, walk-through, practice. All that stuff matters," coach Jason Garrett said. "Certainly physical ability matters, but at that position, so much of it's about decision-making, your impact on other people. When you go in the game, does the ball move? Do you score points? That matters. ... Those guys will get plenty of reps over the course of the preseason."

What they might not get is a lot of reps in the regular season. Prescott, 26, has not missed a game since taking over as the starter in 2016. He has played 3,140 of 3,207 offensive snaps, including 99.4% of the snaps last season.

Rush played six snaps in 2018. In 2017 as a rookie, he threw three passes in two games.

He won the backup job despite being an undrafted free agent because of his preseason work: six touchdown passes, no interceptions. Last season, he had one touchdown pass and four interceptions in the preseason.

"Just wasn't playing as well, just trying to force things probably," Rush said. "You just have to let the game come to you. The competition is everywhere. Just get the ball out of your hand, make the right decisions and just keep moving the chains."

White, a fifth-round pick in 2018, was on the 53-man roster last season but was inactive for every game. In the preseason, he completed 44 of 70 passes for 414 yards but did not have a touchdown pass and had one interception. He remembers walking onto the field at Levi's Stadium for the first time.

"Joe Looney was my center, so I'm like, 'OK, this guy is an NFL veteran. He knows what to do. God forbid something happens, but I'll ask him and he'll tell me what to do,'" White said. "He's like, 'Let's go, Mike.' I remember Coop telling me it's really just like college but everybody else is really, really good. You have to go in with the mindset of: Listen, you've played a lot of football before, just go out there, execute the plays and get the jitters out of you."

It will help Rush and White that those who will be watching them the most intently have been in their shoes before, from Kitna, to Garrett, to offensive coordinator Kellen Moore. They forged their NFL careers as backups, understanding the importance of preseason work.

"You're trying to help them become the best version of themselves," Garrett said. "When you come from the same perspective, that can be helpful to them."

Kitna told the quarterbacks he once had a preseason in which he completed 41 of 52 passes. White said that's their goal now in this preseason. Through nine padded practices in camp, Rush and White have had their share of positive and negative moments. On Tuesday, Rush was intercepted twice and White was picked off once.

In the offseason program, the Cowboys QBs alternated days in which each worked with the starters, but that has not been the case much while in Oxnard, although White got more work with them this week.

"You're still out there competing," Rush said. "You know more. You're kind of out there winging it as a rookie, trying to figure things out on the fly. Now I'm a lot more comfortable with the offense and what NFL defense is about."

Rush and White know one more thing. They can't worry about the enormity of what's at stake.

"If you do, you'll kind of fold," White said. "You just have to go out there and have fun and know at the end of the day you have your goals in mind that you want to reach. But you've got to go out there and cut it loose. You can't play tight or else you won't play good football."