SANTA CLARA -- Christian McCaffrey's early season absence opened the door for Jordan Mason's breakout, while also creating a substantial challenge for the 49ers as rookie Isaac Guerendo is thrust into a prominent role as San Francisco's No. 2 running back.
The 2024 fourth-round draft pick has registered just one carry for zero yards through two games, while Mason has bore the brunt of the 49ers' running game with 48 of the team's 49 rushing attempts by running backs thus far.
While it's difficult to envision Mason maintaining his remarkable efficiency with such a monstrous workload, San Francisco might not have much of a choice due to the difficulty it faces getting Guerendo up to speed with the team's outside-zone heavy run scheme.
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"It's really hard," offensive line coach/running-game coordinator Chris Foerster said after Thursday's practice regarding the challenge of expediting Guerendo's adaption to the 49ers' scheme. "You just have to coach them and you have to have the right kind of guys that can learn on the fly, that can watch other people, learn without taking reps."
Mason has taken the NFL world by storm with his explosive performance to begin the 2024 season, but his success didn't come right away, as the third-year back faced similar struggles early in his professional career.
Foerster explained a major hurdle young running backs in this scheme face stems from cutting back too quickly on zone runs without properly pressing the designated landmarks set by the offensive line blocking in front of them.
"Mason had some problems early when he was getting carries," Foerster said. "One of the primary things in zone running is they want to take the ball and cut back too soon. It happened to all our guys in the game.
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"There's a reason you got to press the line of scrimmage. When you're zone running, when you're double teaming on the line of scrimmage, the runner has to keep pressing the double teams to bring those second-level defenders so you can zone to block them.
"If he cuts back too quick while we're double teaming, the linebacker just goes, 'Oh, I'm going to go make the play.' The runners tie completely together with the line. So if you don't press the line of scrimmage, or can't press the line of scrimmage because there's a whiff and somebody is in the backfield, immediately we can't block second-level defenders."
That critical synchronicity between running back and offensive line was lacking during Guerendo's lone NFL carry in last week's loss to the Minnesota Vikings, with the rookie running back making a premature cut that resulted in the play going for no gain.
A successful zone-run call is reliant on the running back's feel for patiently waiting to explode through the proper running lane, a skill that generally comes with reps that a rookie isn't afforded the luxury of entering the league with.
"Isaac's run, he cut back entirely too quickly," Foerster said. "Sometimes you get the ball and you see this hole. You're like, 'No, no, no. Not yet!' That takes reps, patience to press the line of scrimmage and get to those holes, and eventually they open up. But you have to have that patience, and that's hard to get. You have to watch, you have to study out here in practice, we have to do it. [Running backs coach Bobby Turner] drills it in his drillwork, but there's nothing like those live reps. [Mason] was the same way.
"You can see their helmet stripe. When you watch the All-22, as soon as they get the ball, if they [turn their head] ... not if you're running outside zone. They're looking too soon. You got to press, and then that hole will appear. But if you see that helmet stripe go there, nine times out of 10 they don't go press where they should, and we can't get second-level defenders blocked."
Mason's 48 carries are tied for the NFL's heaviest rushing workload through two weeks, which creates valid concerns about the 49ers not wearing down the third-year back while San Francisco already is without the services of McCaffrey.
Simply put, San Francisco finds itself in quite the conundrum. Guerendo hasn't had time to adequately develop the patience that generally is required to thrive in the 49ers' scheme, but the only way that goal appears attainable is through receiving live reps that San Francisco justifiably hasn't felt comfortable giving the rookie back to begin the season.
Guerendo already has flashed his tremendous physical traits, ripping off a 93-yard kick return during the preseason. Now, he must find a way to pair his blazing speed with the necessary vision to excel in the zone-run calls that perfectly are set up to maximize his natural talent.
As the 49ers continue to weather the storm without the 2023 NFL Offensive Player of the Year, Guerendo's expedited learning curve could be the key to unlocking the full potential of San Francisco's offense for the duration of McCaffrey's stint on the injury list.
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