Williams caught a TD pass and rushed for two scores for the Rams, who avoided their first 0-3 start under Sean McVay in remarkable fashion. Stafford passed for 221 yards, and Tutu Atwell had four catches for 93 yards.

“I think there are the games where you bring just a little bit more juice,” Williams said. “Just the games where you can’t wait to play, when everybody’s doubting you and everybody’s (saying), ‘There’s no way the Rams are gonna win. The Rams are gonna start 0-3.’ We feel it for sure, but it’s something that fuels us.”

Jauan Jennings set career highs with 11 catches for 175 yards and three touchdowns for the 49ers, who blew a lead of at least 14 points for the first time since 2018. While the Rams have salvaged hope for their season, the defending NFC champions were left flustered, frustrated — and under .500 for the first time since Brock Purdy became their starting quarterback in 2022.

The Niners led 24-14 midway through the fourth quarter, but Jake Moody missed a 55-yard field goal attempt for San Francisco with 2:43 to play. Stafford hit Atwell for a 50-yard completion to the San Francisco 5, and Williams took it in two plays later.

Ronnie Bell then dropped a long pass with 1:02 left that would have put San Francisco in field goal range, and Xavier Smith — elevated from the Rams’ practice squad for this game — took his first career punt return 38 yards to midfield.

A 25-yard pass interference penalty against linebacker De’Vondre Campbell put the Rams in range, and their rookie kicker buried the kick.

San Francisco threw several laterals after time expired, but the final play died on the Rams’ sideline.

Purdy passed for 292 yards in the Super Bowl favorites’ second straight road loss after falling at Minnesota last week.

“Plenty of opportunities,” defensive end Nick Bosa said. “I can only speak for myself, and it wasn’t good enough. We’ve got to close them out when we have a chance. … It’s definitely a rough start, but we’ve been through some tough stretches before, but we just have to stay together.”

Both teams were missing most of their top offensive play-makers due to injury. The 49ers played without Christian McCaffrey, Deebo Samuel and George Kittle, while the Rams were without Cooper Kupp, Puka Nacua and Tyler Higbee.

Purdy focused on Jennings, who caught two scoring passes in the first quarter and another in the third to become the first 49ers wide receiver with three TD catches in a game since Terrell Owens in 2001.

The former seventh-round pick had more TD catches Sunday than he managed in the previous two seasons combined, and his total catches and yards were more than both of his two previous best games combined.

“Jauan was unbelievable,” 49ers coach Kyle Shanahan said. “The numbers show it, but more than the numbers, he was a warrior the whole game. He’s always like that. Got a lot more opportunities today, and he was automatic on every single one.”

Jennings’ most impressive grab was a leaping 32-yard catch over Quentin Lake to set up a field goal that put the Niners ahead 24-14.