FRISCO, Texas -- Though Dez Bryant’s tibial plateau fracture in his right leg has captured most of the headlines this week, Dallas Cowboys Pro Bowl left tackle Tyron Smith is listed as questionable for Sunday’s game against the San Francisco 49ers because of a back injury.

Smith did not play last week against the Chicago Bears and is looking at missing two games in a season for the first time in his career. He missed one game in 2012 with an ankle injury before sitting last week.

A week ago Smith was added to the injury report with back tightness after he was unable to finish practice. Though he was listed as questionable for the Bears game, the Cowboys expected him to be able to play, but his back never loosened up.

Smith did not practice this week, but was able to work on the side the last two days. He said Thursday he was feeling better but was not sure he would be able to play against the 49ers.

"I don’t want to get into the details of the procedures that we’ve gone through medically," coach Jason Garrett said. "Suffice it to say that we’ve evaluated him a lot of different ways. He’s making progress. He’s better today than he was yesterday, and so he’ll move around more and we’ll see how he responds to that work."

Garrett said the back injury is unrelated to the stinger issue Smith experienced in training camp, and in the season opener against the New York Giants.

If he can’t play, then Chaz Green would start for the second straight week at left tackle. Ronald Leary is starting at left guard for an injured La'el Collins, who has been ruled out with a toe injury.

In addition to Smith and Bryant being listed as questionable, so are cornerback Orlando Scandrick, who did not play last week because of hamstring strains, defensive end Jack Crawford (shoulder), right tackle Doug Free (quadriceps), linebacker Andrew Gachkar (neck), safety Jeff Heath (knee), and linebacker Mark Nzeocha (Achilles). Quarterback Tony Romo (back) is out.