Starting linemen Marc Colombo and Kyle Kosier, who sustained knee injuries during training camp, missed practice for the second consecutive day Thursday.
"We have a lot of confidence in both Barron and Holland," Phillips said. "They have worked well all along. They are looking forward to this opportunity. They have both started, had some good games. They have shown they can play in the National Football League. I think they want to show they can play for the Dallas Cowboys."
Dallas acquired Barron from St. Louis this summer in a swap of underachieving former first-round draft picks. Linebacker Bobby Carpenter was sent to the Rams, who released him at the end of training camp.
Barron played in 76 games for St. Louis, all but two of them starts, and looks forward to his chance with Dallas.
"This is a great opportunity for me to go out and show what I can do to help the team," Barron said. "My confidence is high. ... It feels pretty normal. Being a starter is a good experience."
Unchanged are center Andre Gurode and right guard Leonard Davis, though Romo doesn't sound too worried.
"We have a lot of confidence in the guys that are stepping up. They're good players as well," Romo said. "Were lucky enough to have some depth at those positions and were going to keep battling."
Copyright 2010 by The Associated Press