The 49ers suffer another 4th-quarter collapse under coach Kyle Shanahan

SANTA CLARA, Calif. — The defense wilted in the heat, the offense couldn't finish drives or protect the ball and the San Francisco 49ers blew another late lead to a division opponent in frustrating fashion.

Brock Purdy threw two interceptions in the second half, Jordan Mason lost a fumble in the red zone and San Francisco allowed Kyler Murray and the Arizona Cardinals to drive for two fourth-quarter scores in a 24-23 loss Sunday that looked eerily familiar to an earlier defeat against an NFC West foe.

Two weeks after blowing a 24-14 lead in the fourth quarter to the Los Angeles Rams, the Niners (2-3) did it again as they couldn't protect a 23-13 advantage against Arizona. This marked the sixth time they have blown a double-digit lead in the fourth quarter in the regular season and playoffs under coach Kyle Shanahan, tied for the most by any coach in the NFL since he was hired in 2017.

“It's super frustrating,” All-Pro left tackle Trent Williams said. “Obviously, we have to figure out how to close out games and how to get teams out early when we have the chance.”

The Niners had plenty of chances to be in control thanks to a blocked field goal that Deommodore Lenoir returned for a touchdown in the first half and an interception by Nick Bosa that set up a field goal.

But San Francisco let the Cardinals hang in the game and pull it out late with Murray throwing a 2-yard TD pass to Elijah Higgins followed by James Conner's 2-point conversion that made it 23-21.

Murray then converted a fourth-and-5 pass under heavy pressure to rookie Marvin Harrison Jr. on the winning drive with the running game doing the rest.

“In the second half, we kind of melted down,” All-Pro linebacker Fred Warner said. “Too much leaky yardage, missed tackles, not fitting it right.”

The blunders by the offense were even more costly. The 49ers settled for field goals three times after getting inside the 10 in the first half. They had another red zone drive in the second half end in a turnover on downs when they went for it on fourth-and-23 because kicker Jake Moody was out with a high ankle sprain.

Then the most costly mistake came when Jordan Mason lost a fumble on first and goal from the 8 with 6:20 to play and San Francisco protecting a two-point lead.

“I just got to be better and more aggressive down there, and collectively as a unit, obviously once we get down there, all of us our mindset man has to be we’ve got to punch this in,” Purdy said. “We know we can settle for a field goal, but we have to hold ourselves to a higher standard, and cross the goal line."

Despite all that, the 49ers still had a chance when they took over at their own 27 with 1:32 to play. Purdy completed a 15-yard pass to George Kittle to get the drive started. But on the next play Jalen Thompson came in unblocked on a blitz and hit Purdy, forcing him into a floater that was intercepted by Kyzir White to seal the win.

After going 11-1 in the division the past two seasons — with the only loss coming when several starters rested in a Week 18 game last season against the Rams — San Francisco has lost its first two NFC West games headed into a showdown with first-place Seattle on Thursday night.

“The standard here is excellence,” Purdy said. "What we’ve proven the last couple of years of the standard of what we can play at, that’s what we’re trying to get to. It’s early in the season and we’re still trying to find our true identity as a team. We’re getting there. It’s a couple of plays away and a couple of drives away from gelling and gluing together. So I’m confident that we’ll find it.