The San Francisco 49ers have boasted one of the NFL's top rushing units almost every year since Kyle Shanahan took over as head coach in 2017. Over the past four seasons, the 49ers ranked top-15 in rushing attempts and rushing yards, and they ranked top-seven in both categories in the two seasons San Francisco made deep postseason runs (2019 and 2021).

And up until they traded for Christian McCaffrey, the 49ers had accomplished all of their rushing success with relatively unknown talent. The team's top-three scrimmage yard running backs over the past five seasons were: Carlos Hyde (a veteran holdover from the Jim Harbaugh era), 2021 sixth-round rookie Elijah Mitchell and three undrafted free agents in Raheem Mostert, Matt Breida and Jeff Wilson Jr.

While all are solid players, that group isn't exactly a dynamic game-changer.

The 49ers tried – and failed – to find their running backs of the future in the draft and in free agency. They spent four picks at the position since 2017 in Mitchell, Tyrion Davis-Price, Trey Sermon and Joe Williams. Only Mitchell has seen extensive snaps. San Francisco also signed Jerick McKinnon to a four-year, $30 million deal in 2018 and Tevin Coleman in 2019 on a two-year, $10 million deal. Neither panned out, though that's mostly due to injury.

Now, finally, Shanahan has his guy in McCaffrey. It cost a lot — 2023 second-, third-, and fourth-round draft picks and a 2024 fifth-round pick — but the deal gives the 49ers perhaps their most dynamic running back ever.

Before even diving into schematics, McCaffrey will join arguably the most versatile skill position group in the NFL. Wide receiver Deebo Samuel is one of the best runners with the ball. Tight end George Kittle is a blocking phenom who can beat linebackers on passing routes. Receiver Brandon Aiyuk has proven his value as a playmaker. Fullback Kyle Juszczyk can run, block and catch out of the backfield.

Add McCaffrey to the mix and it's hard to find a hole in the 49ers' offense outside of Jimmy Garoppolo, which is a different argument for another day.

McCaffrey will be great in the Shanahan offense

When it comes to style, this is where things get fun. The highly touted Shanahan offense employs a wide-zone blocking scheme that effectively forces defenders to play laterally while the offensive line opens up running lanes where the offense wants. McCaffrey is a perfect fit for that because he can make plays between and outside the tackles and adjust on the fly. Just look at his rushing charts over the years.

His quickness is sudden. McCaffrey is a home-run hitter almost every time he touches the football. He has the second-most games with a run or reception of at least 50 yards since 2017, according to Panthers.com, and the third-most yards per touch since 2017 at 5.78 yards. McCaffrey has also led the NFL with 113.6 scrimmage yards per game since 2017.

McCaffrey's propensity for pass-catching gives him something the Shanahan offense has severely lacked as well. The only 49ers running back with more than 50 receptions in a season during Shanahan's tenure was Hyde in 2017. Juszczyk, the fullback, has also led 49ers running backs in receptions three times over that span but he has never finished with more than 33 in a season. McCaffrey, meanwhile, averages six receptions for 51.4 yards per game – both of which lead the NFL since 2017 – and has caught at least 80 balls in seasons he has played a full slate of games.

These skills should create matchup nightmares for the 49ers because they can utilize McCaffrey in their two-back sets (21 personnel), as well. San Francisco led the league in that grouping in three of the past four seasons, according to Sharp Football Analysis, and was second behind the New England Patriots in 2020. In this lineup, McCaffrey could be a runner, a receiver, a blocker or some combination of all in any given play. That's incredibly difficult for a defense to plan against.

McCaffrey should eat in this offense and give the 49ers a weapon they've never had during the Shanahan era. Samuel's role as a pseudo-running back in 2021 was probably the closest thing San Francisco had to McCaffrey, and that helped vault the team to an NFC championship game and the cusp of another Super Bowl appearance. Now, they have someone who plays that role full-time.

The knocks against this move are threefold: McCaffrey's injury history, the contract that comes with him and what San Francisco gave up to Carolina.

McCaffrey played just 10 games from 2020-2021 after never missing a game in his career. He'll cost at least $11.8 million against the cap from 2023-2025, per Over The Cap. The 49ers also gave up the equivalent of the fourth overall pick, according to PFF, for a 26-year-old running back with more than 1,200 career touches.

This could blow up in the faces of Shanahan and general manager John Lynch, especially considering the huge questions surrounding their decision to trade up for quarterback Trey Lance last year and his current injury predicament. McCaffrey is not a lock to play a full season and the team might not be able to afford to keep some of its best pieces in the coming years or find talent in the draft after spending so much on him.

But after failing to return to the Super Bowl two years after their magical 2019 run, this was the move the 49ers needed to make to give them the advantage over the rest of their division, their conference and the NFL. McCaffrey is one of the truly special talents in the league, and Shanahan will surely know how to properly utilize him to create a dominant offense given McCaffrey's skills.