INGLEWOOD, Calif. — In his address to his team Saturday night, San Francisco 49ers coach Kyle Shanahan issued a stern warning about the kind of opponent the Los Angeles Rams would be on Sunday.

Even though the winless Rams were fresh off an embarrassing loss to the Arizona Cardinals and had more injuries than any other team in the league, Shanahan expected Los Angeles to play with plenty of verve and desperation.

“You have to take away their hope,” Shanahan said. “If you give (Rams quarterback Matthew) Stafford too much hope and you end up putting the ball in his hands, 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 building to a 14-point lead, special teams mistakes, defensive errors and offensive blunders prevented San Francisco from building on its early momentum and suffered a surprise 27-24 loss.

The Niners lost their second straight game, falling to 1-2 and losing to an NFC West Division opponent for the first time when Brock Purdy was starting quarterback. After the game, Shanahan described his team as “pissed” that a win had slipped away from them. That frustration was palpable in the locker room, as wide receiver Jauan Jennings, who nearly led the Niners to victory with a career-high passing yardage, declined to speak to the media.

“That was unacceptable,” linebacker Fred Warner said. “We can’t afford that. We can’t beat ourselves up. We can’t make mistakes like that again. All three phases have to play better. We’ll look at the tape, fix it and move on.”

A proud 49ers team that has been to at least the NFC Championship Game in four of the last five years has a lot of improvement to make. 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, as they are also missing many injured players.

The game took a turn for the worse for San Francisco with 6:22 left in the second quarter when the Rams faced a fourth-and-six on their 43-yard line. Trailing by two points and with little to lose, this was an obvious opportunity for a fake punt, so Shanahan and the Niners called the punt return in anticipation of a fake.

It didn’t matter, because the direct snap to Rams running back Ronnie Rivers turned into a 7-yard gain and ultimately the Rams’ first touchdown. Instead of a possible three-point deficit, the Rams still had plenty of hope. This was only strengthened by San Francisco’s continued blunders on special teams.

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 had to accept a 38-yard punt return that set up the Rams’ game-winning field goal.

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

Special teams weren’t the only problem for the Niners on Sunday. A defense that limited the Rams to zero points, 29 yards and one first down in the first quarter allowed Los Angeles to score 27 points, 267 yards and 18 first downs in the final three games. The Niners also didn’t force a turnover when Stafford made his 45th game-winning drive in the fourth quarter or overtime, the seventh-most since the merger in 1970.

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 get over the loss,” end Nick Bosa said. “We can’t just go on and pretend everything’s OK … The NFL is up and down, and no matter how talented you think you are, you have to play well on Sunday.”

Despite all of this, the Niners still had a chance to win, thanks in large part to Jennings and Purdy. Jennings, starting in place of Samuel, had a memorable game with 11 catches for 175 yards and three touchdowns, becoming the fourth player in franchise history to record 175 receiving yards and three touchdowns in a game.

Purdy, on the other hand, was in great shape even without his usual weapons, completing 22 of 30 passes for 292 yards and three touchdowns with a passer rating of 137.1. Those numbers could have been better, however, as Purdy didn’t get much help from pass receivers not named Jennings. The Niners were charged with three drops, but others were negated by penalties.

None was bigger than the long pass Purdy threw to an open Ronnie Bell on the right sideline with 1:08 left. Purdy’s pass was on target and Bell had a clear chance to make a big catch and set up a potentially game-winning field goal. Instead, Bell dropped the ball and the Niners had to punt to set up the Rams’ final drive.

With the loss, Purdy became the third 49ers signal caller (along with Joe Montana and Steve Young) to lose a game in which he completed at least 70 percent of his passes and three or more touchdowns, and it was also the first time the Niners fell below .500 with Purdy as the starter.

At 1-2, the Niners are well aware that there is still plenty of time left in the season. Their locker room is full of players who have helped them get out of even tougher situations in the recent past. But they also know that opportunities like Sunday’s can come back to haunt them later in the year.

“That’s just part of the NFL and when you’re 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 the best opportunity of anybody. It’s the NFL and we all have to be realistic. We have to have the mindset to go out and get it every Sunday and nothing is ever given to us.”