Stepping in for the injured Christian McCaffrey, Mason, known as JP inside the organization, seized the opportunity, rushing for a career-high 147 yards and a touchdown, leading the 49ers to a convincing Week 1 victory.
Head coach Kyle Shanahan spoke to reporters via a conference call on Tuesday, highlighting Mason's evolution since joining the 49ers as an undrafted free agent in 2022.
"As soon as he got here, he hit the hole every single time," Shanahan said. "A lot of times, when he first got here, he was so used to getting so downhill every play that he missed a number of runs to get outside. And to be able to coach him and him actually get better and not worse was really cool too because sometimes when you've got a coach running backs too much, with a remote in your hand, it kind of takes away their natural instincts.
"JP, to be such a downhill runner, but when the defense gives him the look to go outside, he doesn't really hesitate with it. He takes it. So that's been really cool with him."
Despite not having a high draft grade on Mason, the 49ers liked what they saw and brought him on as a free agent. Shanahan initially had concerns about Mason sharing carries at Georgia Tech, but those worries faded when he learned Mason was sharing the backfield with eventual Alabama transfer and future first-round pick Jahmyr Gibbs.
Mason has consistently risen to the challenges in Santa Clara. Although it didn't come into play against the Jets, Mason has been inspired by McCaffrey's versatility. In fact, he invested $3,000 in a JUGS machine to improve his pass-catching skills.
Mason's 28 carries on Monday were a career-high and the most by a 49ers running back since Frank Gore's 31 carries against the Cleveland Browns in 2011.
"This was the first time he got a number of carries," Shanahan said. "It's tough to get those in our offense when you've got guys like Christian and guys like [WR] Deebo [Samuel] and stuff. But this was his opportunity, and everyone saw how he did. That's why it was much easier to just keep feeding him the rock."
With McCaffrey's status uncertain for the upcoming game against the Minnesota Vikings, all eyes are on Mason to see if he can build on his breakout performance and continue contributing to the team's success.
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