SAN FRANCISCO -- For a while, the Giants appeared destined to be doomed by another night of defensive ineptitude. But with a little inspiration from rookie catcher Joey Bart, they found a way to flip the script. 

Bart breathed life into the Giants’ dugout with a sixth-inning pep talk and then hit the first of three home runs off All-Star closer Josh Hader to ignite a six-run rally in the bottom of the ninth that propelled San Francisco to a stunning 8-5 win over the Brewers on Friday night at Oracle Park.

The Giants trailed, 5-2, heading into the bottom of the ninth, but they pulled within one on solo shots from Bart and pinch-hitter Darin Ruf and then capped their improbable comeback on a walk-off grand slam by Mike Yastrzemski.

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It was the Giants’ first walk-off home run since August 2020 and their first walk-off grand slam since Bobby Bonds did it in 1973. It also marked the first time in MLB history a team hit three homers in an inning including a walk-off grand slam, according to Stats by STATS.

“Only time will tell, but I think that was a really good reminder that we should never give up,” Yastrzemski said. “We should always keep our minds in the game and just keep playing no matter what happens because the mistakes that we’ve made somebody else can make them or we can just get right in the game by swinging the bats really well.”

The miraculous finish salvaged what had otherwise been a frustrating night for the Giants.

LaMonte Wade Jr. gave San Francisco a 2-0 lead with a two-run triple off Brandon Woodruff in the second inning, but Milwaukee surged ahead with a five-run, two-out rally in the fifth that was prolonged by several defensive miscues by the Giants.

Left-hander Alex Wood opened his final start before the All-Star break with four scoreless innings and then struck out Luis Urías and Pedro Severino to start the fifth, but the Brewers’ offense began to stir when Kolten Wong shot a single just past a diving David Villar at third. Jonathan Davis followed with a grounder down the third-base line that looked like it might roll foul, but it stayed fair after bouncing over the bag, allowing Davis to beat out Villar’s throw for an infield single.

The floodgates swung open when Wade booted Christian Yelich’s routine ground ball to the right side, allowing Wong to score from second and cut the deficit to 2-1. Wade’s error prompted manager Gabe Kapler to lift Wood and bring in submariner Tyler Rogers, who walked Willy Adames to load the bases and then surrendered a three-run double to Andrew McCutchen.

The Brewers added another run on Urías’ bases-loaded walk to stretch their lead to 5-2, draining morale in the Giants’ dugout. That’s when Bart decided to speak up. The 25-year-old turned to veteran Curt Casali and told him that the team had to keep fighting, a message that ended up resonating throughout the entire dugout.

“It was actually really refreshing,” Yastrzemski said. “It felt like the energy was sucked out of the dugout. I think it just kind of grinded Joey’s gears. He was just a little fired up that there wasn’t any positive energy at the time. It was really good to hear and really good to kind of see him fired up like that. It wasn’t towards anyone, and it wasn’t aggressive. He was just like fed up.”

“As a young player, I don’t feel like it’s really my role to try and go and speak out, but that’s just how I was feeling at the time,” Bart said. “Like, ‘Hey, it’s not over yet. Let’s keep going, let’s find a way to win.’ And magic happened, for sure.”

Bart led off the ninth with a no-doubt shot off Hader, hammering an inside sinker halfway up the left-field bleachers to kick off the Giants’ decisive rally. After returning to the dugout, Bart continued to stoke the Giants’ belief by immediately strapping on his shin guards to prepare for the possibility of extra innings.

“It’s almost like good luck,” Bart said. “I’m not going to leave them off.”

The Giants continued to feed off his confidence, with Ruf adding another monster, pinch-hit blast to left-center field to make it 5-4. Austin Slater followed with a single -- his fourth hit of the night -- Yermín Mercedes reached on a hit-by-pitch and Thairo Estrada added another single to load the bases with one out. That brought up Yastrzemski, who drove a first-pitch sinker out to right-center field to win the left-on-left matchup with Hader and complete the epic comeback.

“It was probably the wildest one of my whole career, to be honest,” Wood said. “Three bombs off Hader in the ninth? I still don’t believe it. It was just crazy. We needed it. The boys pulled it off, and hopefully we’ll carry some good momentum the next two days.”

Hader's struggles on Friday came just two days after his last ineffective outing, when he did not retire a single batter and allowed a three-run, walk-off homer to Jose Miranda in a loss in Minnesota.

The four-time All-Star was asked if he is healthy, and he said, “Yeah.”

When asked if he was hurting at all, Hader replied, “No.”

“I feel like I’m trying to feel things I don’t need to and I lost the aggressiveness that I normally have,” said Hader. “So, it’s just little things. But I’ve just got to move on and bring it tomorrow.”