The Niners had rolled to a 31-13 win but an already banged-up team had just lost five key players to injury, the most serious of which is "most likely" a torn left ACL for star defensive end Nick Bosa.
There was also a sprained right ankle for quarterback Jimmy Garoppolo, a sprained knee for running back Raheem Mostert and knee injuries to defensive tackle Solomon Thomas and running back Tevin Coleman. None finished Sunday's game.
The 49ers are also awaiting the return of tight end George Kittle (sprained knee), cornerback Richard Sherman (strained calf), receiver Deebo Samuel (foot) and defensive end Dee Ford (neck), none of whom was active on Sunday.
All of which left Shanahan once again preaching the importance of every player on the roster in a season that could slip away fast if depth doesn't emerge.
"I just told the guys we do have a good team, but there’s also so many guys in our place that can get a lot better, coaches and players," Shanahan said. "And when you lose some good guys like we did and it will probably be for a while, we need guys to get better. There’s a number of guys who can improve on our team, and that’s what we’ve got to focus on doing."
If there's a silver lining to be found in all the injuries, it's that turning to the deepest reaches of the roster for production is nothing new for this group. Last year, on their way to an NFC title, the Niners seemed to suffer one or two key injuries every week. When tackles Joe Staley and Mike McGlinchey went down, unknowns such as Justin Skule and Daniel Brunskill filled in well. The same was true for tight end Ross Dwelley stepping in for Kittle and fullback Kyle Juszczyk.
This year, it starts with quarterback Nick Mullens, who is no stranger to replacing an injured Garoppolo. Mullens started eight games for Garoppolo in 2018 and posted a passer rating of 90.8. On Sunday, he completed 8 of 17 passes for 71 yards with an interception while mostly managing the game to get to the end. Although Shanahan said Garoppolo could still play next week against the New York Giants, it's hard to imagine him playing through a high ankle sprain on the same MetLife Stadium playing surface the Niners believe did them no favors on Sunday.
"Coach Shanahan says it at the start of the season and pretty much every week," Mullens said. "Everybody has a role on this football team, all 53 of us can help the team get better in one way or another, and that's more true now than it has been."
Mullens won't be the only new face in the lineup. Veteran Kerry Hyder Jr. is likely to step in for Bosa, though the Niners could add more bodies at the position until Ford and Ronald Blair III return. Rookie defensive tackle Javon Kinlaw got more work after Thomas departed, and Kentavius Street and Kevin Givens will also factor into the mix more. Suddenly, the 49ers' dominant defensive line lacks both depth and star power, which means the rest of the team will have to pick up the slack.
At running back, it's Jerick McKinnon who stands to get the most work, though Jeff Wilson Jr. figures to get some opportunities. That doesn't even account for players such as tight ends Jordan Reed and Dwelley, cornerback Ahkello Witherspoon and receivers Brandon Aiyuk and Mohamed Sanu, all of whom should get more snaps because of injuries.
"We’ve got a lot of depth, and over the years, Kyle and [general manager] John [Lynch] have created the team that they have, and guys are ready to step up," linebacker Fred Warner said. "I think not only the guys who had to step up today, everybody in the locker room can get better."
Coincidentally, it's McKinnon and Reed, who had combined to miss three full seasons before getting on the field this year, who could play integral roles in keeping the Niners' above water while players heal. Reed scored two touchdowns Sunday in Kittle's stead and McKinnon scored his second touchdown in as many weeks to go with 77 rushing yards.
"When you go through things, you gain experience," defensive end Arik Armstead said. "We have been in situations like this before where our guys were going down and guys were forced to step up, and that’s what we’re gonna have to have."