ST. PETERSBURG -- On the brink of monumental frustration, the Rays got a monumental walk-off victory. But make no mistake: Thursday afternoon’s 6-5 12-inning victory against the Athletics at Tropicana Field -- the Rays’ second straight walk-off win -- was no walk in the park. In fact, it was as improbable as they come.

Richie Palacios’ one-out single to right field off reliever T.J. McFarland, the Athletics’ seventh pitcher, brought in automatic runner José Caballero from third base, giving the Rays their triumph. Ben Rortvedt’s groundout had moved Caballero from second base to third.

“They brought in an extra infielder, so I was looking to lift a ball to hit to the outfield,’’ said Palacios, who entered the game in the 10th inning as a pinch-runner for Yandy Díaz. “This was just baseball, sticking with it, finding a way to win.’’

“You’re going to create energy when you play tight games and find ways to win them,’’ Rays manager Kevin Cash said. “Everybody played a role to allow us to get this done. That’s kind of the way we’re built. We’ve got a lot of hitters who might not be in the starting lineup on a nightly basis, but they can come up and have the biggest at-bat of the game.’’

Rays center fielder Jose Siri, one night after his home run-robbing catch and walk-off single propelled a win, played the biggest role of all with a two-homer performance.

In the ninth inning, after the Rays had gone hitless in six consecutive innings, Siri delivered a one-out game-tying homer off Athletics closer Mason Miller, who had converted each of his previous 11 save opportunities. The Rays then fell behind 5-4 in the 10th, but got another tying run off Miller to extend the game once more.

Siri’s ninth-inning homer came on a 100 mph pitch from Miller, making him the first Ray since pitch tracking started in 2008 to homer on a pitch of that velocity in the regular season. (The previous high: Austin Meadows off Red Sox right-hander Nathan Eovaldi, 99.6 mph, on Sept. 12, 2020.)

“He throws between 100 and 103 miles an hour, so I was trying to stay as short as I could,’’ Siri, who also hit a Statcast-projected 428-foot solo homer in the second, said through team translator Manny Navarro. “We all know he throws hard. I was just trying to connect however I could.’’

Miller had his first career blown save after surrendering his first homer since 2023.

“We all know what Mason Miller has been doing, and he has built up a special season,’’ Cash said. “[Siri] got a fastball down and hit it a long way. He has given us a lot of energy with his performance on both sides of the ball.’’

“Looking back over it, I wish I had gone somewhere else [in the zone], obviously,’’ Miller said. “But that’s where I was trying to execute. I underestimated him after that first swing. He got to that ball in on his hands and put it out of the yard.’’

The RBIs by Siri and Palacios were attention-grabbing, but the victory was set up by the Rays’ bullpen (including bulk pitcher Tyler Alexander, who followed opener Shawn Armstrong), which didn’t surrender an earned run in the final 9 1/3 innings.

In the 11th inning, after A’s automatic runner Shea Langeliers advanced to third, Garrett Cleavinger got a strikeout and a groundout. In the 12th, with runners on second and third, Richard Lovelady got a strikeout and a popup.

“Both of those guys were outstanding,’’ Cash said. “To prevent guys from scoring when you get the lead runner starting at second base, that’s a really tough ask for a pitcher. But our guys handled it well tonight. Ultimately, keeping them off the board [in the 11th and 12th innings] is what led to us winning a game.’’

Lovelady (1-3) said he hopes the Rays, who dropped six of the first seven games to start the nine-game homestand, can build on their newfound momentum.

“We’re in the 12th inning trying to hang on, and we’ve got one guy left [in the bullpen],’’ Lovelady said. “You’re just trying to put the fire out. As a reliever, your mindset is just get it done, no matter the score, no matter the situation. We had been scuffling, so these were two big wins.’’

The dramatic comeback allowed the Rays to take two of three games in the series, providing momentum as they face this season’s initial meeting against the Orioles on Friday night. Aaron Civale is scheduled to make the start. After that, who knows?

After using seven pitchers Thursday, Cash said the status of his bullpen was “not good.’’ He meant usage, not performance. But after two straight walk-off wins, the Rays are feeling better about themselves.

“Hopefully we can carry this through to the road trip,’’ Cash said.