SAN ANTONIO – As the old saying goes, you can’t make the club in the tub. That’s especially true when your replacement runs with the opportunity.

With Lonyae Miller impressing coaches on a daily basis, Tashard Choice could be in trouble or trade bait.

Miller might have made a run at the third running back role even if Choice had stayed healthy. But the 6-foot, 232-pound second-year running back has really taken advantage of the extra reps he’s getting because of injuries to third-round pick DeMarco Murray and Choice, who strained his calf on the opening day of camp and is expected to miss 2-4 weeks.

“If someone goes down, you’ve got to step up and fill their shoes,” Miller said after a strong performance in Sunday’s Blue-White scrimmage, when he scored a couple of touchdowns. “I feel like I’ve done that.”

Actually, it’s not just about filling Choice’s shoes. Miller has a chance to prove that he’s a better fit on the Cowboys’ roster than Choice.

Choice has been productive in limited opportunities with the ball in his hands, rushing for 1,064 yards and eight touchdowns on 222 carries and catching 53 passes for 426 yards in three seasons. However, he struggles in pass protection and on special teams, with owner/general manager Jerry Jones publicly pointing out the latter flaw.

Miller, who went undrafted after backing up San Diego first-round pick Ryan Mathews at Fresno State, showed after being promoted from the practice squad in December that he could contribute on special teams. He’s opened eyes with his powerful slashing running style in camp, but he’s really impressed coaches as a pass protector.

“The biggest area I think he’s improved is recognizing the defensive fronts when it comes to pass protection,” running backs coach Skip Peete said. “He’s done a lot better in that aspect. He’s done a good job of picking up blitzes. He’s just playing very physical right now.”

Miller’s talent has always intrigued the Cowboys. He’s a big back who ran a 4.43 40-yard dash and put up 26 225-pound bench press repetitions during his pre-draft workouts.

But Miller struggled during his rookie training camp, playing hesitantly and making a lot of mental mistakes. That’s no longer a problem for the lone tailback who attended all of the Cowboys’ player-run offseason workouts.

Miller not only knows his assignments, but he’s displayed an advanced understanding of the offense. He’s been an effective runner in part because he’s done an excellent job of setting up his blocks. As Miller said, he’s playing faster and smarter.

“The light has kind of come on,” Peete said. “He’s playing with a lot more confidence. We knew he was a good runner. Now he’s taking his instincts and doing what he has to do to help the play be successful."

Added head coach Jason Garrett: “As much as anything else, he’s matured. The physical ability was always there.”

If Miller keeps this up, it’s likely that Choice’s run with the Cowboys is coming to an end.