ST. LOUIS – A fiery superstar who has tormented himself most of the season for not delivering enough for the slumping Cardinals, Nolan Arenado finally allowed himself to enjoy his 10th-inning trip around the bases on Wednesday night as fireworks exploded high above Busch Stadium.

For one night, at least, Arenado was able to brush aside the offensive struggles both he and the Cardinals have been mired in most of the season after he hit a walk-off grand slam that lifted St. Louis to a 10-6 win over the rival Brewers.

After lacing a Trevor Megill curveball into the seats in left field, Arenado calmly circled the bases before firing his helmet to the turf and hopping his way into a mob of teammates circling home plate for a celebration. For Arenado, it was his 14th home run of the season, his fifth career walk-off homer and the sixth grand slam of his illustrious career. The Cardinals, who came into the night having lost seven of eight games, won on a walk-off for the third time this season.

“It’s been tough, and I haven’t come through the way that I would like, and I had a really poor at-bat in the ninth, so it just felt really good to come through for the guys,” said Arenado, who pushed his RBI total to 59 on the season. “It just felt good to come through. If I didn’t come [through] there, I don’t know how people would look at me anymore. At the end of the day, I’m just trying to do my best.

“I haven’t been helping us win as much as I would like, but today was a really good day.”

A night after dropping the series opener between the two NL Central rivals, St. Louis beat Milwaukee for just the second time this season. The Brewers, who started the day with an 11 1/2-game lead in the National League Central and a 12-game cushion over the Cardinals, swept the Cards at Busch Stadium over a three-game series in April and then won three of four in Milwaukee in early May.

Cardinals manager Oliver Marmol is hopeful that Arenado’s blast is the spark that the Cardinals need to put together a strong closing kick that might get them back into playoff contention.

“That was a big swing that could lead this group in a lot of ways moving forward,” said Marmol, who tapped second-year slugger Luken Baker to pinch-hit in the seventh inning before he delivered a game-tying, two-run home run. “We needed that. … For Nolan to do what he did in the 10th, that could be very meaningful moving forward. I loved every second of it.”

Matt Carpenter and Tommy Pham drew bases-loaded walks in the bottom of the ninth inning against Brewers’ star closer Devin Williams to knot the game at 6. Williams, a St. Louis native who closed out Milwaukee’s 3-2 victory on Tuesday, allowed a hit and two earned runs while walking three and striking out two in two-thirds of an inning in Wednesday’s ninth inning.

The blast by Baker, who was promoted from Triple-A Memphis on Tuesday, tied the game at 4 after the Cardinals’ bullpen allowed two runs in the top of the seventh. That clutch hit, combined with a gritty ninth inning where the Cards got the game tied against one of the best closers in baseball is a sign of the fight still left in the club, Marmol said.

“With [Joey] Ortiz’s ball to the wall [in the top of the eighth inning], you could easily just fold there and go, ‘Here we go again,’ but that’s the last thing on their minds,” Marmol said with conviction. “They’re resilient. … I mentioned it [on Tuesday]. This group is not going to give in. I love this group. They’re going to fight and give it their best shot. They did exactly that tonight.”

Arenado’s game-winning moment likely would not have been possible without Baker pinch-hitting for Brendan Donovan and lacing a ball into the bullpen for a game-tying homer in the seventh inning. Asked afterward if he got the souvenir baseball to commemorate his best moment in the big leagues, Baker cracked: “That was like the fourth coolest moment of the night for us.”

Baker deferring to Arenado as Wednesday’s hero spoke to just how much the eight-time All-Star has struggled to deal with the Cardinals’ offensive struggles this season.

“It still weighs on you and it’s not so much about what people are saying, but what you are telling yourself,” Arenado said. “The performance speaks for itself. I’m just trying to change the narrative and do the best that I can. I like where my mind is. I’m in that ‘flow’ state and I’ve got to stay there.”