49ers roster: What role will Kerryon Johnson have in 2021?

The 49ers added another running back to their depth after losing a key contributor at the position for the rest of the season.

With Raheem Mostert opting for season-ending surgery to get his knee fully healed, the San Francisco 49ers are adding former Detroit Lions running back Kerryon Johnson to their practice squad.

But as fans of the team are well aware, running backs on the Niners practice squad don’t often find themselves there for long, especially with the return of the COVID-related practice squad rules from 2020 for this season.

This begs the question: What role, if any, will Johnson have for San Francisco in 2021?

The Lions selected Johnson with the 43rd overall pick of the 2018 NFL Draft out of Auburn, and during his three years in Detroit, Johnson rushed for 1,225 yards on 283 carries with eight touchdowns in 34 games. He also caught 61 passes for 527 yards and three more touchdowns, a skill that will make him useful in head coach Kyle Shanahan’s offense.

Johnson was never the bell-cow of the Lions’ offensive attack, although he did lead the team in rushing his rookie year with 641 yards over 10 games, and again in his second campaign, although this time with just 403 yards in eight games.

But his final year as a Lion, he was pushed out by Adrian Peterson and rookie D’Andre Swift, leading to Johnson to rush for just 181 yards even though he played all 16 games for the first time in his career.

To be fair, the Lions running attack during his tenure there was putrid, finishing in the bottom half of the league in Football Outsiders’ DVOA metric in 2018 (minus-13.2 percent, 19th), in the bottom six in 2019 (minus-18.3 percent, 29th), and the bottom half again last season (minus-13.8 percent, 21st).

These numbers suggest that although Johnson wasn’t a great running back, the Lions had bigger problems than just the guy running the ball.

As a matter of fact, those same DVOA numbers paint a solid picture of the player that Johnson can be.

Why 49ers can be optimistic about Kerryon Johnson

Johnson finished fifth in the league for running backs with over 100 carries in DVOA during his rookie season with 17.5 percent, but he fell to 41st in his second season at minus-13.7 percent and didn’t have enough carries to place last season.

So, he certainly can be a useful player for Shanahan and his offense, but that doesn’t mean he’ll step in and be a starter.

Rookie Elijah Mitchell earned the opportunity to be the lead back for as long as he’s doing the job, fresh off his 104-yard debut against the Lions on Sunday.

Related Story: How Raheem Mostert injury shakes up 49ers depth chart

But the depth beyond Mitchell includes fellow rookie Trey Sermon, who despite being selected in the third round of the 2021 NFL Draft, was a healthy scratch against in Detroit, second-year undrafted free agent JaMycal Hasty, who scored on his only carry of Sunday’s game, and now Johnson, while they wait for the return of Jeff Wilson off the PUP list after the 49ers matchup against the Indianapolis Colts on Oct. 24 at the earliest.

In other words, Johnson, if he’s elevated off the practice squad, may find himself getting an opportunity to play, even though that may not be until Week 3 at the earliest given the later date of his signing.

While the 49ers certainly hope for the best for Mostert, the next-man-up mentality has already kicked in at the running back position in 2021.

Johnson may soon find himself as part of that group.