MINNEAPOLIS -- The San Francisco 49ers are certain that they'll be without running back Christian McCaffrey for at least the next three games. And while it could be longer than that before McCaffrey returns from Achilles tendinitis, coach Kyle Shanahan said Sunday it's too soon to make that determination.
"Nobody knows," Shanahan said. "We're dealing with tendinitis so, not one person knows. He doesn't know. We don't know and [we will] take it day by day."
While backup running back Jordan Mason continued to produce Sunday, the Niners undoubtedly could have used McCaffrey in a 23-17 loss to the Minnesota Vikings. Despite piling up 399 yards of offense, the Niners were limited to 17 points as they finished a combined 3-of-13 on third and fourth downs, gave up six sacks and were 2-of-4 in the red zone.
The Niners placed McCaffrey on injured reserve Saturday afternoon as he continues to deal with calf and Achilles issues. At the center of the problem for McCaffrey is Achilles tendinitis that has been hard to predict on a day-to-day basis. Asked Sunday whether McCaffrey would need surgery, Shanahan said "not that I've been told."
On Thursday, McCaffrey had what Shanahan called his "worst" day in terms of dealing with the tendinitis while he practiced on a limited basis. That flare up kept McCaffrey out of Friday's practice altogether and ultimately led to the decision to send him to injured reserve.
The earliest McCaffrey could return would be the Oct. 10 game against the Seattle Seahawks in Seattle, though that is on Thursday night which would mean a short week and an artificial playing surface in his first game back.
According to Shanahan, the decision to put McCaffrey on IR was made, at least in part, as a way of forcing everybody to slow down and not try to rush him back. The NFL's reigning Offensive Player of the Year has been adamant about playing, declaring in each of the past two weeks he'd be ready to go despite outside doubters.
"By putting him on IR, it's at least four weeks," Shanahan said. "It'll give him some time to rest and protect him from himself. Us too. No matter how he's feeling."
Absent McCaffrey and Elijah Mitchell (who is out for the year with a hamstring injury), Mason made his second career start on Sunday. He again filled in well, rushing 20 times for 100 yards with a touchdown, becoming the first player since Aaron Jones in 2017 to rush for 100-plus yards in each of his first two career starts.
"[He] just does what he's been doing since he's been here," Shanahan said of Mason. "We've had two guys go down already, so I think it's pretty obvious that he knows he's starting when that's case."
But Mason isn't the threat McCaffrey is when it comes to running routes and catching passes. In 2023, McCaffrey was third in receptions (67), second in receiving yards (564) and first in touchdown catches (seven) among all running backs. In his two starts this season, Mason has two catches for 9 yards.
McCaffrey's versatility, especially in combination with wideout Deebo Samuel, opens up a dimension to San Francisco's offense that few teams can match.
"Christian is the offensive MVP for a reason," tight end George Kittle said. "He has an incredible impact on this team. Just him being around, he boosts everyone's confidence. I still think we had opportunities to find a way to win today and we just didn't. But yeah, it's just there's things that we can't do without Christian."
Shanahan initially announced McCaffrey's injury on Aug. 6. At the time, Shanahan said they hoped McCaffrey would miss a couple of weeks, not participate in any preseason games and then be ready for the season opener against the New York Jets.
That plan seemed to be coming to fruition as McCaffrey was seen running on the side within a few weeks after the injury and returned to practice in the week before the Sept. 9 win against the Jets.
But McCaffrey was a surprise scratch from that game despite his insistence a few days before that he would play. On Wednesday, McCaffrey explained that he mentally tells himself every week he's going to play as a means of self-motivation.
On Thursday, McCaffrey did not fare well in practice and by Friday afternoon, Shanahan and general manager John Lynch were openly discussing the potential to place him on injured reserve.
Sunday's loss to the Vikings counts in the four games McCaffrey must miss while on injured reserve. He's also definitely out next week against the Los Angeles Rams, on Sept. 29 against the New England Patriots and on Oct. 6 against the Arizona Cardinals.