With Christian McCaffrey and Jordan Mason watching from a suite in Levi's Stadium, rookie running back Isaac Guerendo led the San Francisco 49ers backfield in his first start in Week 14.

The fourth-round pick rose to the challenge superbly, going for 128 yards from scrimmage and two touchdowns as the 49ers crushed the Chicago Bears 38-13.

However, the 49ers now face a nervous wait to see if Guerendo can play in Thursday's game with the Los Angeles Rams. 

Guerendo headed back to the locker room with around six minutes left in the fourth quarter and did not return to the game. 

Afterward, head coach Kyle Shanahan revealed Guerendo is believed to have suffered a foot sprain, though X-rays were not conclusive.

The former Wisconsin and Louisville back will have further testing on Monday.

"I thought Isaac looked real good today," Shanahan said. "Hopefully we get some good news on that injury."

In his absence, Patrick Taylor Jr. scored the final touchdown, with Ke'Shawn Vaughn getting garbage time work. 

Should Guerendo be unable to go in a crucial NFC West matchup, then Vaughn would almost certainly be elevated from the practice squad again and join Taylor and Israel Abanikanda, who was inactive on Sunday having been waived by the New York Jets.

Kyle Shanahan shuts down bizarre trade rumors with simple statement after 49ers’ blowout win

That should be the end of it.