PITTSBURGH -- The numbers for the Cubs’ offense in Monday night’s series opener against the Pirates were astronomical.

18 runs.

21 hits.

Eight stolen bases.

The 18-8 rout of the Bucs at PNC Park was a sight to behold, and it set all kinds of season and franchise marks.

• The Cubs had not stolen eight bases in a game since June 9, 1913, against the Brooklyn Dodgers, per the Elias Sports Bureau.
• The last time any Major League team had 21 hits and eight stolen bases was June 28, 1912, when the New York Giants did so against the Boston Braves in a 12-3 win, per STATS.
• The Cubs’ 21 hits and 18 runs were both season highs. The last time the Cubs had 18 runs and 21 hits came in the same game: a 20-9 victory over the Reds on Aug. 1, 2023, when they also had 21 hits. It was the third time since 2022 they had reached both marks in a single game, though they didn’t accomplish the feat in any contest between 1996-2021.

But the blowout wasn’t a given through five innings. The Cubs had to chip away at starting pitcher Mitch Keller. Against him, they racked up seven of their eight stolen bases, including three by Pete Crow-Armstrong in the eight-hole. That loosened things up for No. 9 batter Miguel Amaya, who extended his recent tear at the plate with an RBI single in the second.

“It’s fun when you know you’re on their mind, because the job is about making the next guy’s life a little bit easier,” Crow-Armstrong said. “That’s what that does, and that’s the best part about that.”

The constant pressure chased Keller after four innings and brought in Domingo Germán. The Cubs only had a 3-2 lead, far from the huge margin they’d create. But in the sixth inning, they rallied in their biggest frame of the year.

Dansby Swanson walked, Crow-Armstrong singled and then took off for his third stolen base. But Amaya’s second of four hits nullified that feat, as it turned Crow-Armstrong’s hustle into a second run on Amaya’s double.

Germán got two strikeouts, then put Seiya Suzuki quickly into a two-strike count. But Suzuki roped one of his four hits to keep the inning going -- and in retrospect, it was bigger than the four-run lead it gave Chicago.

“I thought Seiya’s hit was the big hit of the game,” manager Craig Counsell said. “It made it [6-2], and then the floodgates kind of opened up after that.”

Three straight batters reached after Suzuki to bring Swanson up a second time in the inning, and he crushed a grand slam to effectively seal the decision. It was the first time this season the Cubs had put up eight runs in an inning, and the first time they’d done so since Sept. 19, 2023 -- which was also eight runs against the Pirates, though in the eighth inning.

“That’s definitely a first -- hitting a grand slam in your second at-bat of the inning -- for me,” Swanson said. “It just goes to show just the depth of the lineup and the guys to put professional at-bats together no matter what the score is, no matter what the situation is.”

The Cubs never slowed down. By the end of the night, every batter in the starting lineup had a hit and eight had at least one RBI.

But it began with a tight affair, putting pressure on the basepaths and finding ways to extend at-bats and chase the starter to begin the chase for all kinds of history.

“Look, you knock the starter out in the fourth, that’s good offense and you’re going to make them use their whole staff there -- and that’s what you want to do,” Counsell said. “It’s hard to do that. It’s hard to knock a pitcher out like that in the fourth inning. We got 95 pitches, I think by the fourth inning.

“That’s good offense. It’s good at-bats. It’s getting on base. And we did a really nice job with that tonight.”