A somber chord was struck in the 49ers locker room on Sunday night. This is a team that had just won 33-17 and moved to 8-4 on the season after resoundingly beating one of the AFC’s top contenders.

But the reality set in; the knowledge that Jimmy Garoppolo, a well-loved figure who’d reclaimed his starting and leadership statuses after a tumultuous offseason, was out for the season.

For the second time this year, San Francisco has lost its starting quarterback. It happened just 10 yards away, on the same hash as the spot Trey Lance’s season ended in Week 2. It was a right ankle injury for Lance, a right foot injury for Garoppolo.

With Garoppolo’s injury, there’s an understanding that the bigger picture of competing for a Super Bowl will likely become a substantially more difficult task. It already was.

Brock Purdy played very well on Sunday. He has much more to prove.

But beyond that knowledge, there was the human component because of the person Garoppolo is.

Garoppolo has been through astonishingly low valleys and near-pinnacle peaks with the 49ers.

There was the electrifying, five-game introduction in 2017 which brought hope to an organization sorely in need of it. Three games into 2018, it all collapsed on an awkward fall down the left sideline against the Kansas City Chiefs.

The Super Bowl run followed, punctuated by that overthrow of Emmanuel Sanders and the nauseating ever-so-closeness of the loss.

COVID-19 and a historic rash of injuries derailed the 2020 campaign. The 49ers made their move to go get Lance, the man who was (or is) to replace Garoppolo.

When the move for Lance went down, Garoppolo asked merely for a chance to compete for his job in that 2021 season. He got it, and won.

After a 3-5 start to the season and considerations of a quarterback change, he reclaimed his standing and the 49ers made an astonishing NFC Championship run which ended, ignominiously, with an evaporated 10-point lead and loss to the division rival Rams.

The 49ers were done with Garoppolo. He teared up in his postgame presser. He said his goodbyes. All the while crediting the people around him.

No one made any mistakes about the plan in the offseason. There was perhaps too much openness about what was to proceed.

Garoppolo would rehab, and be traded.

But the rehab didn’t take. He needed shoulder surgery. And the 49ers got stuck standing at the end of a particularly wild game of QB musical chairs.

Garoppolo had nowhere to go. And as the deadline to cut him loomed and no suitors emerged, John Lynch and Kyle Shanahan — someone who has never shown an inclination to make a decision for the sake of popularity, or been afraid to live within uncomfortable situations — proved they were not bluffing.

They kept him. They’d been snakebitten by injuries at the quarterback position for far too long, and Garoppolo was far too capable to throw aside for some cap space. With a 22-year-old at the helm, it didn’t hurt to have someone with whom you knew what you were getting.

And aside from a stinker against the Denver Broncos, and a couple duds against the Atlanta Falcons and Kansas City Chiefs, Garoppolo was playing well.

This was shaping up to be the best season of his career. He hadn’t thrown an interception in five games. The 49ers had won four-straight with sole ownership of the top spot in the NFC West.

He was delivering those on-time, over-the-middle balls he’s had an elite knack at hitting on, especially under pressure. There were still misses outside the hashes, but he started moving the chains on third downs. He was decisive.

He was even making some off-schedule throws you normally didn’t see from him. His on-the-run throw down the right sideline to Ray-Ray McCloud against the Chargers (he also had one for a touchdown to McCloud against the Chiefs), and touchdowns to George Kittle (one against Arizona, and one in the back of the end zone against the Rams) stand out.

It’s not just that he’d played well.

It’s that, throughout the entire process of the 49ers openly announcing that they didn’t believe Garoppolo to be good enough to win them a Super Bowl and that they wanted to deal him, he was a professional.

Throughout all of last season, and the multitude of times it has seemed obvious Kyle Shanahan does not fully trust his capabilities at quarterback — often for good reason — he’s been, unflappably, himself.

Since he arrived, it’s been apparent that Garoppolo is an exceedingly likable, low maintenance guy. It’s not uncommon for teammates to vouch for their starting quarterback, but the visible excitement for Garoppolo when he won that game in Week 2 belied the fraternity between him and the veterans he’s grown with.

George Kittle, one of Garoppolo’s closest friends on the team, maligned, most of all, the fact that Garoppolo won’t be at the facility.

“It’s sad. It sucks. Especially losing him from the building for a while, that’s going to be tough,” Kittle said. “He’s one of the heartbeats of this team. He’s a guy that a lot of guys look up to. He’s just a constant for us. He plays at a high level, gets the guys going. He’s a great leader. So just losing that will be tough.”

The leaders of the locker room were distraught.

Shanahan told the team at halftime, with Kittle saying players made their rounds to the training room to give Garoppolo their condolences and support.

Trent Williams’ voice wavered as he recalled finding the news at halftime.

“Everybody had a lump in their throat finding out what happened to Jimmy,” Williams said. “I’m crushed, man. I’m crushed. Jimmy is like a brother to me. He’s such a good guy, such a great teammate, such a good soul. Great guy to be around. I was crushed.”

It’s a crushing blow in the story of Garoppolo that seemed to be crescendoing amidst such unexpected circumstances. Earlier in the day, NFL Network’s Ian Rapoport had reported he and the 49ers were both open to a potential reunion in the offseason, when Garoppolo hits free agency.

His story isn’t over, but it has taken yet another brutal dive into the unknown. Without him, the 49ers will dive with him into that murk. San Francisco controls its own destiny, but it was once again reminded, unceremoniously, that life in the NFL if nothing if not brutal and unpredictable.