ENGLEWOOD, Colo. -- Denver Broncos wide receiver Emmanuel Sanders was a question mark going into last week’s preseason opener against the Seattle Seahawks, and he’s a question mark going into Sunday’s preseason game against the San Francisco 49ers.

Sanders, who had sat out Monday’s practice before participating in Tuesday’s and Thursday’s work, was held out of Friday’s morning practice with a thigh injury.

“I don’t know, we just take it one day at a time,’’ said Broncos head coach John Fox. “We thought the smart thing to do was to hold him out of practice [Friday]. We’ll see what tomorrow brings.’’

It was a bit of a surprise Sanders played in the preseason opener after missing time with the injury -- he ended up playing 20 snaps in the 21-16 Broncos’ victory. And given the injury has flared up again, the Broncos may consider the most prudent move to be keeping him out of the 49ers game.

Following Sundays game, the Broncos will practice for three days against the Houston Texans next week before a Sept. 23 game against the Texans. The Broncos starters will likely play into the third quarter against the Texans.

Against the 49ers, the starters are expected to play into the second quarter.

Linebacker Danny Trevathan (lower left leg) and running back Montee Ball, who is returning from an appendectomy, did not participate. Defensive end Chase Vaughn (right knee) and defensive end Greg Latta (right hip) were again held out of practice.