INGLEWOOD, Calif. — When he addressed his team Saturday night, San Francisco 49ers coach Kyle Shanahan issued a stern warning about the type of opponent the Los Angeles Rams would face on Sunday.

Though the Rams, who had yet to win a game, were coming off an embarrassing loss to the Arizona Cardinals and were as injury-riddled as any team in the league, Shanahan expected Los Angeles to play with a sense of urgency and desperation.

“You’ve got to take away their hope,” Shanahan said. “You give (Rams quarterback Matthew) Stafford too much hope (and) you put the ball in his hands at the end, that’s not a situation you want to be in.”

Unfortunately, that was exactly the situation the Niners found themselves in late Sunday afternoon. Despite jumping out to a 14-point lead, San Francisco couldn’t build on its early momentum due to special teams miscues, defensive breakdowns and offensive errors en route to a stunning 27-24 loss.

The Niners lost their second straight game, 1-2, and for the first time lost to an NFC West opponent with Brock Purdy as their starting quarterback. After the game, Shanahan described his team as “pissed off” at how a victory had eluded them. That frustration was evident in the locker room as wide receiver Jauan Jennings, who had nearly led them to a victory with a career-best outing, refused to speak to the media.

“It was unacceptable,” linebacker Fred Warner said. “We can’t do that. We can’t beat ourselves. We can’t make those kinds of mistakes again, all three phases have to play better. We look at the tape, fix it and move on.”

A proud 49ers team that has reached at least the NFC Championship Game in four of the last five years has plenty of fixing to do. The Niners entered Sunday without a trio of their best players — injured star running back Christian McCaffrey (Achilles tendinitis), receiver Deebo Samuel (calf) and tight end George Kittle (hamstring) — but the Rams had little sympathy because they are missing a ton of players themselves.

Sunday’s loss deepened with 6:22 left in the second quarter and the Rams facing a fourth-and-6 from their 43. Trailing by two scores and with little to lose, it was an obvious spot for a fake punt, so much so that Shanahan and the Niners called the punt return with the expectation of a fake punt.

It didn’t matter, as the direct snap to Rams running back Ronnie Rivers resulted in a gain of 7 yards and ultimately the Rams’ first touchdown. Instead of a potential three-score deficit, the Rams were left with plenty of hope, a hope only heightened by San Francisco’s continued special teams blunders.

After allowing a blocked punt in last week’s loss to the Minnesota Vikings, the Niners allowed a fake punt conversion, missed a 55-yard field goal and gave up a 38-yard punt return, setting up the Rams’ winning field goal.

“That’s where I thought we had a chance to run away with it, not give them any hope,” Shanahan said. “That gave them a lot of hope. They got back into it … those are three big plays in the game.”

Special teams weren’t the only problem for the Niners on Sunday. A defense that held the Rams to no points, 29 yards and one first down in the opening quarter allowed Los Angeles to score 27 points, 267 yards and 18 first downs in the final three. The Niners also didn’t force a turnover, as Rams quarterback Matthew Stafford recorded his 45th game-winning drive in the fourth quarter or overtime, the seventh-most since the 1970 merger.

The 14-point comeback win is the Rams’ biggest under coach Sean McVay and the biggest overall since Week 2 of the 2012 season.

“I think we have to feel the loss,” Nick Bosa said. “We can’t just go on and pretend it’s okay. … The NFL, it goes up and down and no matter how talented you think you are, you have to play well on Sunday.”

Despite all that, the Niners still had a chance to win, thanks in large part to Jennings and quarterback Brock Purdy. Jennings, who replaced Samuel, delivered a game to remember, throwing 11 catches for 175 yards and three touchdowns, becoming the fourth player in franchise history to have 175 receiving yards and three scores in the same game.

Purdy, meanwhile, didn’t miss a beat without his usual weapons, finishing 22 of 30 for 292 yards and three scores with a 137.1 passer rating. But those numbers could have been better, as Purdy didn’t get much help from pass catchers not named Jennings. The Niners were charged with three drops, though they erased others with penalties.

None of those things were bigger than the deep pass Purdy fired to an open Ronnie Bell on the right sideline with 1:08 remaining. Purdy’s pass was on target, and Bell had a golden opportunity to make a big catch to set up a potential game-winning field goal. Instead, Bell dropped the ball, forcing the Niners to punt to set up the Rams’ final drive.

With the loss, Purdy became the third 49ers quarterback (joining Joe Montana and Steve Young) in franchise history to lose a game in which he completed at least 70 percent of his passes and scored three or more touchdowns, pushing the Niners below the .500 mark for the first time with Purdy as the starter.

At 1-2, the Niners know they have plenty of season left. The locker room is full of players who have helped them out of even tougher situations in the recent past. But they also know that opportunities like Sunday’s could come their way again later in the year.

“That’s just part of the NFL and as a professional in a professional sport, everyone is really good,” Purdy said. “Last year means absolutely nothing. And every time you show up on Sunday, you get everyone’s best shot. It’s the NFL and we all have to be honest about that. We have to have the mentality to go out there every Sunday and take it and nothing is ever going to be given to us.”