Short-handed San Francisco 49ers lose RBs Elijah Mitchell, JaMycal Hasty, Trey Sermon to injury i...

PHILADELPHIA -- The San Francisco 49ers didn't intend to use newly acquired running back Trenton Cannon in any role other than special teams on Sunday. As it turned out, they had no choice but to plug him into the offense.

By the end of San Francisco's 17-11 victory against the Philadelphia Eagles, the Niners had lost their top three running backs to injuries in a span of about five minutes. That came after starter Raheem Mostert was lost to a season-ending left knee injury last week against the Detroit Lions.

First, it was starter Elijah Mitchell's right shoulder, then it was an ankle injury forJaMycal Hasty,and finally it was a concussion for rookie Trey Sermon. Mitchell departed after a 1-yard touchdown run was overturned with 11 minutes, 4 seconds to go, and Hasty and Sermon were out by the 5:45 mark.

Hasty and Sermon did not return to the game, while Mitchell reentered with 5:26 to play. After the game, Niners coach Kyle Shanahan said that the hope was Mitchell's injury was just a stinger and wouldn't be anything that lingers long term.

Mitchell is slated to have further tests done when the team returns to the Bay Area.

"He said he was good enough to come back in, so that's when you think it's a stinger, but until you have time to go and get an MRI and stuff like that, you never know," Shanahan said. "But we're hoping it was just a stinger. You usually feel good about it the way he was talking and the way he was able to come back in the game."

The Niners finished with 117 yards on 38 carries, an average of just 3.1 yards per attempt on a day in which every yard was difficult to come by.

After rushing for 104 yards in his NFL debut last week, Mitchell started in Mostert's place but struggled to get much going on the ground, as the Niners' offense didn't get on track until late in the first half. Mitchell finished with 17 carries for 42 yards and had two catches for 11 yards.

Hasty had the most success of the Niners' runners, carrying five times for 38 yards to go with four catches for 21 yards. Sermon gained 8 yards on his lone carry but suffered a concussion when he took shoulder and helmet shots to the head on the attempt.

Sermon will immediately go into the concussion protocol and must clear it before he can return to the field. Shanahan was unsure of the severity of Hasty's ankle injury after the game, and he, too, is set for further tests back in the Bay Area.

In between Hasty's and Sermon's exits and Mitchell's return, Cannon carried once and lost 1 yard to put a cap on a whirlwind week in which the 49ers claimed him off waivers from the Baltimore Ravens on Wednesday.

"He's only been here since Wednesday and we dressed him to help us out on special teams today," Shanahan said. "And from what I saw he did a hell of a job and we weren't expecting him to go in at running back, but I think he did go in and I'm just glad he knew what to do."

Depending on the status of Mitchell, Hasty and Sermon come Wednesday's practice, the 49ers could need to add another back to the mix. Veteran back Kerryon Johnson could be one option if needed after he was signed to the practice squad last week.