It’s C.J. and the walk-ons for the Broncos’ running game.

Come to think of it, C.J. Anderson was also the NFL equivalent of a walk-on last season.

The Broncos’ running back group has been thinned like never before after Montee Ball re-strained his groin Sunday against the St. Louis Rams.

Ball will miss the next two or three weeks, according to two NFL sources. Another running back,Ronnie Hillman, is expected to miss another game with his left midfoot injury Sunday when the Broncos play the Miami Dolphins.

Ball was a second-round draft pick in 2013 and Hillman was selected in the third round of 2012. Anderson was an undrafted rookie signed out of Cal last year. His backups are undrafted rookies Juwan Thompson of Duke and Kapri Bibbs of Colorado State.

The Broncos have a little more NFL experience on their practice squad in Jeremy Stewart, who played sparingly for the Oakland Raiders the past two seasons.

Meanwhile, the Broncos have not ruled out tight end Julius Thomas from playing against the Dolphins, even though he suffered a sprained left ankle in the first quarter Sunday against the St. Louis Rams and did not return.

Thomas said he hurt it while blocking on a running play. The back of his legs got rolled up by running back C.J. Anderson as he fought for 1-yard gain with 2:27 left in first quarter. Thomas left and didn’t return. He spent the rest of the game in the visiting trainer’s room.

He’s not in a boot, which is encouraging. He was able to slip on a basketball shoe, which is also encouraging. He walked through the locker room without a noticeable limp.

“I knew it was something that wasn’t going to end my season,” Thomas said. “I’m day to day.”

Wide receiver Emmanuel Sanders likely will miss practice this week after he suffered a concussion Sunday against the Rams. Sanders will go through the concussion protocol, and his status against the Dolphins will be a matter of whether he is cleared later in the week by an independent doctor.