SAN DIEGO -- Fernando Tatis Jr. hit a go-ahead, two-run home run with two outs in the eighth -- two innings after the Padres scored seven runs -- and San Diego stunned the Chicago Cubs 9-8 Monday night.

On the 20th anniversary of the first Padres game at Petco Park, Tatis exuberantly celebrated the moment that fully erased an 8-0 deficit. He held his bat out with his left arm as he watched the ball sail into the left-field seats, flipped it, hollered and pumped his fists as he started his trot. He was wearing custom cleats honoring the late Hall of Famer Tony Gwynn. Rookie Jackson Merrill was aboard on a leadoff walk off Adbert Alzolay (1-1).

"It was amazing. But all credit to the boys," Tatis said. "We were down 8-0, and we were never out of the game. We kept building, we kept taking good at-bats against tough pitches. The boys started executing. We started moving the line, we kept believing in each other and that was just the final blow."

The win tied the Padres' largest comeback in franchise history. The other three games they won after trailing by eight runs: May 23, 1970, at the San Francisco Giants; June 10, 1974, versus the Pittsburgh Pirates; and July 8, 2021, versus the Washington Nationals.

The Cubs, meanwhile, entered Monday having won 234 consecutive games they led by eight or more runs. Their last such loss came on June 28, 2002, at the Chicago White Sox.

In conjunction with his branding company Xample, Tatis plans to unveil 50 pairs of custom cleats this season. His choice for Monday night, featuring different designs on each cleat, honored Gwynn, known as Mr. Padre, who played his entire 20-season career in San Diego. Gwynn died in 2014 at age 54.

"Definitely the shoes," Tatis said with a laugh. "The power came from above. Always grateful. Definitely a little bit inspired today. I'm going to keep playing with them. Hopefully, they keep sending good luck. Just happy I was wearing those shoes today."

As Padres manager Mike Shildt said, "It was a big homer. Impressive. Impressive guy. Real proud of him."

Tatis slammed into the wall in right after just missing Dansby Swanson's two-run triple in the fourth that gave the Cubs an 8-0 lead.

Shildt said Tatis came up to him in the dugout and said, "Man, just a game of inches."

"I said, 'Yeah, sometimes things don't work out and we've got to keep fighting.' This was when it was 8-0," the manager explained, "and he said, 'Don't worry, we're going to keep fighting,' and he patted me on the back."

Wandy Peralta (1-0) got the win and Robert Suarez the save, his fourth.

Cubs right-hander Javier Assad, who grew up across the border, in Tijuana, took a two-hit shutout and an 8-0 lead into the sixth before the Padres pulled within a run in the sixth that was highlighted by two-run homers by Jake Cronenworth and Xander Bogaerts. The Padres had five hits, a walk and an error that inning.

Assad allowed a leadoff walk to Tatis before being chased by Cronenworth's two-run homer -- his first of the season -- to right. Jose Cuas came on for Chicago, and the next three Padres batters reached, starting with Manny Machado on an error by shortstop Swanson that made three of the runs unearned. Ha-Seong Kim smacked a two-run triple, and Luis Campusano hit an RBI grounder. Bogaerts capped the scoring with a two-run shot off Luke Little for his first homer of the campaign. Tatis flied out to right to end the inning.

Assad allowed two runs and three hits, with seven strikeouts and three walks.

San Diego's Yu Darvish, who pitched for the Cubs from 2018 to 2020, threw 42 pitches in the second inning, when the Cubs scored four runs on three hits, two walks and a hit batter. Darvish twice loaded the bases, and Ian Happ and Cody Bellinger each hit a two-run single.

Darvish got through a quick third inning but was done for the night after allowing four runs and four hits while striking out four and walking three. It was just the 10th time in 281 career starts, including the postseason, that Darvish went three or fewer innings.

The Cubs then jumped on Pedro Avila for four more runs in the fourth. After the Cubs loaded the bases with one out, Bellinger hit a sacrifice fly, Christopher Morel hit an RBI double and Swanson tripled in two more.

ESPN Stats & Information and The Associated Press contributed to this report.