But that's exactly how things transpired after the third-round pick Sermon was an unexpected healthy scratch and Mostert left the game early due to a knee injury.
Mitchell, who was selected in Round 6 of the 2021 NFL Draft out of the University of Louisiana, finished the day with 19 carries for 104 yards, with one of those carries going for a 38-yard touchdown. Mitchell was impressive for the 49ers during training camp and the preseason when he was healthy, so his success when given the opportunity didn't come as a big surprise to head coach Kyle Shanahan.
"I thought he did a real good job," Shanahan said. "That's kind of what we expected him to do. But it's always tough in your first game and stuff. He went in there and didn't hesitate and ran the ball well."
Mitchell's involvement wasn't something many outside of 49ers facilities expected given the fact Sermon was seemingly higher in the pecking order during the preseason. But Shanahan said Sermon's status was never etched in stone, as was demonstrated on Sunday.
"We rotate everybody with the ones, twos and threes throughout camp and stuff. Nothing is ever firm, to tell you the truth," Shanahan said.
Also suiting up along with Mitchell and Mostert was second-year back JaMycal Hasty, who finished with a three-yard touchdown run and one catch for 15 yards.
"We only dressed three backs," Shanahan said. "You always try to do four, but those were the three after doing training camp and stuff that we felt were the three we were going to go with."
Mitchell told reporters after the game he was ready when his name was called on Sunday due to the teaching he's been given by running backs coach Bobby Turner.
"I was definitely ready for it. Coach Bobby T, he coaches everybody the same and keeps us all ready to go because things happen," Mitchell said.
And while he gave an assist to Turner for keeping him ready, Mitchell also gave some props to his blockers for helping him on his touchdown run -- which is certainly warranted given the size of the hole he was given to run through.
"As soon as I caught the ball, I saw George [tight end George Kittle] and them on the outside blocking their butts off," Mitchell said. "I saw the hole so I just had to hit it."
Related News
More San Francisco 49ers News
-
Christian Kirk trending toward 49ers debut, say Kyle Shanahan and Brock Purdy
The San Francisco 49ers opened wide receiver Christian Kirk's practice window last week but decided he wasn't quite ready to return from injured reserve as he continued recovering from a calf injury. Kirk has been a full participant in practices this week as the 49ers prepare... -
49ers' John Lynch admits trade talks are heating up ahead of deadline
Will the San Francisco 49ers make a move before the NFL trade deadline? General manager John Lynch offered no hints about the team's plans during his Friday morning interview with Bay Area radio station KNBR. However, he acknowledged that trade discussions are heating up as the... -
49ers safety Malik Mustapha still playing with chip on his shoulder
Malik Mustapha has come a long way since his days as an overlooked high school football player. But even now, as a safety for the undefeated San Francisco 49ers, he hasn't forgotten where he started or the people who doubted he could make it. Mustapha was a zero-star recruit... -
49ers' Corliss Waitman is Proving His Value Beyond the Numbers
The San Francisco 49ers haven't needed to punt very often this season. When they have, Corliss Waitman has consistently helped them win the field-position battle. Through five games, Waitman has punted just 16 times, largely because of an offense that has moved the ball...