FRISCO, Texas– Sporting the No. 3 jersey number, veteran quarterback Mark Sanchez was on the practice field with his new teammates, less than 24 hours after officially signing to become the Cowboys' backup quarterback.

For now, Sanchez will back up rookie Dak Prescott as head coach Jason Garrett told reporters on Monday that "Sanchez has to be ready." He will be the No. 2 quarterback for Sunday's regular-season opener with the Giants at AT&T Stadium.

Currently, Tony Romo remains on the active roster as the third quarterback but Garrett said Romo will continue to get tests on his back, which has a fractured vertebra bone. There is still a chance the Cowboys could place Romo on the 8-Week IR, but if that happens, it'll be in the next few days.

Sanchez, who the sixth overall pick of the Jets in 1999, has 72 career starts (35-37 record), including two last season with the Eagles. He was signed in the offseason to compete for a starting job in Denver, but lost the battle to Trevor Siemian.

[embeddedad0]"Mark's been a good player in this league. He's been a starting quarterback," Garrett said of Sanchez. "He's been to the playoffs as a starting quarterback. He's started a lot of games. He was a very successful college quarterback. We played against him in our division so we've seen him up close. He's an experienced guy who has a lot of ability. He can move around. He can throw the football He'd had success in the league. We thought it was a good opportunity to add to the depth of our quarterback position. When he was available certainly it was a good opportunity for us to bring him here."

Injury notes for Monday's practice included defensive end Charles Tapper, who hasn't practiced since early in training camp with a back injury. He's getting close to a full return but Garrett said he wasn't expecting the rookie to participate in team drills on Monday.
Linebacker Mark Nzeocha (Achilles) was not practicing in full.
This time of year always brings out a few number changes as the roster got trimmed down to 53 players. Cornerback Dax Swanson switched from 28 to 23, while Tapper went from 79 to 75. His change was expected considering offensive tackle Chaz Green also wore 79 on the offensive side of the ball.