ARLINGTON, Texas (AP) - There are some young blockers in front of Dallas Cowboys quarterback Tony Romo.

Second-year center Phil Costa filled in for an injured five-time Pro Bowler in the first preseason game. And Costa was alongside two rookie starters.

The Cowboys released veteran starters Leonard Davis and Marc Colombo before camp. Offensive line coach Hudson Houck says the Cowboys are moving guys around to see what they can do.

Tyron Smith, the ninth overall pick in April, is expected to start at right tackle. Fourth-round pick David Arkin started at left guard against Denver with Montrae Holland hurt.

Rookie center Bill Nagy got some snaps at left guard in practice this week.