CHICAGO -- The Wrigley Field crowd was buzzing even before the pitch was thrown to Nelson Velázquez, the decibel level rising rapidly with anticipation. By the time the baseball was swallowed by a sea of delirious fans in the left-field bleachers, the old ballpark was shaking.

Velázquez trotted around the bases amid the roar around him on Tuesday night, his first career grand slam having just punctuated an improbable comeback rally in the third. It highlighted an eight-run outburst that sent the Cubs well on their way to a 14-9 victory over the Mariners at the very Friendly Confines.

“I couldn't help but just smile. It was so pure,” Cubs shortstop Dansby Swanson said of the atmosphere. “The energy was just amazing. As soon as Nelly hit that ball -- I hadn't really felt too many things like that in my career.”

For the new-look North Siders, who used the winter months to inject their roster with a long list of veterans with plenty of hardware and rings on their collective résumés, the past two nights have been a step forward in forging their identity. Dramatic wins early in a season can only help that process.

• After emotional day, Swanson takes himself out of game

Monday night was a 3-2 win in 10 innings, when Nico Hoerner's walk-off single helped erase the gut-punch, game-tying homer by Jarred Kelenic in the ninth. After the game, veteran catcher Yan Gomes made Hoerner don a sheriff's hat during interviews. Hoerner passed the hat to Velázquez on Tuesday night.

"Teams come together in certain moments," Cubs manager David Ross said. "And having some fun is always key."

This time around, Chicago's lineup quickly went to work to overcome a rough start by rookie Hayden Wesneski.

With one out in the second, Wesneski stood behind the mound, his head hung for several seconds, as Ross made the trek from the dugout to pull the young pitcher. Seattle had built a 7-0 advantage, capitalizing on a rare lapse in command by the righty.

"I do think it's important to have comeback wins," Cubs president of baseball operations Jed Hoyer said. "Comebacks are a measure of the kind of unity and toughness [you want in a team]. You want a team that's going to keep fighting, clawing, even when you're behind."

Hoyer made those comments before Tuesday's game, when he held court with reporters near the home dugout. In the third inning, he swung by the Marquee Sports Network booth for an in-game interview, watching as his pregame words proved prescient.

By the end of the third, the Cubs had swung the momentum and had the Wrigley Field faithful fully engaged once again. The home half of the third featured 13 batters, who poured out eight runs on eight hits, including homers by Trey Mancini and Velázquez. Swanson collected two of his four hits on the night in the frame.

“You feel like you let the team down, and you feel like you set your team up for a loss already in the second inning,” Wesneski said. “To see them [come back], man …”

It was the first eight-run or eight-hit inning for the Cubs since they matched those numbers in the first inning against the Pirates on May 16 of last season. According to ESPN Stats and Info, the win snapped a 79-game streak during which the Cubs lost every game in which they trailed by at least seven runs.

Ross said he felt his ballclub was still very much in the game as he headed out to lift Wesneski and ask the bullpen to shoulder a heavy load. With the flags atop the old scoreboard in center rippling out, the game had the makings of a vintage Wrigley Field affair.

"We've got way too good of a team," Gomes said, "way too good of a culture, way too good of a fan base that's behind us every single game, to hang our heads. I feel like we've built a team that can, from top to bottom, can really do this. We've got a lot of experience here."

“We continue to preach that to the new guys,” Ross said. “It's not like we're in one of these ballparks that it's hard to put up big, big crooked numbers when the wind’s blowing out here. It's a good place to hit, and I really liked our matchups.”

Mancini said it also helps that the dugout is stocked with veterans who have been through plenty of comebacks in their respective careers.

“We've all been part of crazy games like this,” Mancini said. “We've been around enough to know that you're never out of it.”

Velázquez -- who only unpacked his bags Monday after arriving from Triple-A Iowa -- said he had to calm himself down as he felt the volume increasing in the stadium as he worked to a 3-1 count in the third. The frenzy that followed was hard for him to describe.

“It was something incredible,” Velázquez said.