ARLINGTON, Texas -- The Dallas Cowboys know Dak Prescott will be their starting quarterback when the season begins, but they might not know who their backup is after Saturday's 20-14 loss to the Houston Texans.

Garrett Gilbert started his third straight preseason game but played just two series before being replaced by Cooper Rush, who completed 10-of-12 passes for 97 yards and two touchdowns in the first half.

"Well, we have one more week and we're going to need it," coach Mike McCarthy said when asked if the Cowboys know whether Gilbert or Rush will be Prescott's No. 2.

He acknowledged the Cowboys are always on the lookout for players, especially during this time of training camp.

As for Prescott, McCarthy said the quarterback "hit the target" in a pre-game throwing workout as he continues to work back from a latissimus strain that has kept him out of team drills since July 28. Prescott threw a little more than the 46 to 50 prescribed throws before the game.

"Had a chance to watch it and I thought he looked good, and the most important thing is how he feels afterwards," McCarthy said. "I thought he had another good day and the opportunity of going back to back is important. Still continue to build up on the volume of throws."

Prescott is expected to be a full go for Week 1 against the Tampa Bay Buccaneers, a source told ESPN's Stephania Bell on Saturday, confirming an NFL Network report. He has had no setbacks and remains on track with a progressive throwing program designed to increase his volume of work, the source said.

McCarthy said Prescott will do more in practice next week, but he was not ready to say it would be a full load of first-team reps. He will not play in the fourth preseason game, Aug. 29, against the Jacksonville Jaguars.

That will allow the Cowboys the opportunity to continue to evaluate Gilbert, who completed 3-of-5 passes for 30 yards before being replaced by Rush.

Gilbert has taken all of the first-team snaps in practice since Prescott has been out, but McCarthy said the coaches wanted to even out the snaps on Saturday. On his second snap, Gilbert was tripped as he backed away from the center. On his third snap, he was sacked and lost a fumble that the Texans turned into a touchdown.

"Obviously wasn't his best night," McCarthy said.

Rush, who served as Prescott's backup from 2017 to 2019 but attempted only three passes, threw touchdown passes of eight yards to Tony Pollard and nine yards to Cedrick Wilson. He dealt with back and shoulder injuries in camp that limited some of his work while the Cowboys were in Oxnard, California.

He knew he would play in the first half against the Texans, but not exactly when.

"It's always an uphill battle," Rush said. "You're competing every game. You're always hanging on. You're always trying to get a roster spot, get the two spot. That's kind of the mentality for every guy in here and me especially. Just try to get in there, get your reps and capitalize on those reps in games or practices and always out here just trying to make the team."

Gilbert has completed 19-of-34 passes for 214 yards with no touchdowns or interceptions in the preseason but has not led the offense on a touchdown drive yet.

"We're getting down to crunch time here," McCarthy said. "It's time to start making some decisions."