ST. LOUIS -- Beneath the flashy smile, youthful exuberance and a bubbly energy as he celebrates the successes of his teammates burns an intense fire inside of seething rookie shortstop Masyn Winn.

While he is delighted to have been promoted to the big leagues as a 21-year-old rookie, Winn has been anything but happy with how he’s performed offensively. It’s bothered him so much that he’s already started to think how different he’ll look and how much better he’ll perform when the Cards see him next season.

“I usually drop about 10 or 15 pounds a year, so I want to come in pretty heavy next year and hopefully keep it on throughout the year,” said the 5-foot-10 Winn, whose Cardinals thumped the rival Reds, 15-6, on Saturday at Busch Stadium. “I showed up [to Spring Training] at 185 [pounds], so I want to show up at 190 to 195 next year. I think it's healthier for me over a full season. I mean, if I can sit around 180 to 185 rather than 170 to 175, I think it'd be really good for me.”

Winn, the No. 1-ranked prospect in the Cardinals’ farm system at the time of his promotion to the big leagues per MLB Pipeline, has been everything the club hoped for and more defensively at shortstop. However, Winn has struggled mightily at the plate, leading him to believe that more weight and strength will help him be more competitive against big league pitching. Winn started slowly at the plate on Saturday, but he had an impressive opposite-field two-run single late in the night off All-Star Reds closer Alexis Díaz.

“You definitely want to end on a good note and feeling good about where your swing is at, and Masyn has done a really nice job of that,” Cardinals manager Oliver Marmol said. “Those [opposite-field] hits are what we’ve been talking about, where he’s not trying to do too much. And whatever the game is giving him, he’s taking it. That last at-bat was perfect, where he drives in a couple and stayed on that ball to right field.”

After the game, Winn admitted, “I needed those [RBIs],” given the long stretches where he’s had trouble finding holes for hits. He will head into Sunday’s season finale hitting .176 with two homers, two doubles and 12 RBIs. Those numbers, of course, run directly counter to the hitting that helped Winn make it to the big leagues.

With many of the Cardinals’ middle infielders competing in the World Baseball Classic, Winn opened eyes in Spring Training by hitting .333 with a .949 OPS, two homers, two doubles and two triples in 18 games. He opened the season in Triple-A, and despite a slow start, he hit .288 with 18 homers and 61 RBIs in 105 games. That hitting, combined with his exceptional fielding and his 80-grade arm, earned him an Aug. 18 promotion to St. Louis.

Then, came the offensive struggles that left Winn seething and already plotting how things will be different next season. To mask his frustrations, Winn has often poured himself into his defense.

“I don't really have much of a choice; I’ve got to go play defense, and I don't have time to pout out there,” Winn said. “I do kind of like playing angry, though. I've never been the type to play defense sad. I've always been the type to play mad. When I'm mad and somebody takes a hit away from me, I'm trying to take a hit away from somebody else. I mean, I really don't have time to pout and be sad for myself, so I have to find ways to channel that energy.”

Marmol loves how Winn has channeled his energy toward his defense, making what he called “two to three plays a night to change a game.” Marmol added that there’s “zero concern” about Winn’s ability to hit big league pitching, feeling the young shortstop will be infinitely more advanced next season for having gone through what he has in 2023.

“He tried to do too much early on, but he’s up to 10 walks now, he’s not chasing as much and he’s controlling the strike zone better, staying through the middle of the field and getting his base hits to right,” Marmol said. “We’re starting to see a little more of what we saw in spring. That was just a matter of him slowing the game down and not pressing.

“I’m not concerned with Masyn putting together a good year offensively. He controls his emotions as good as anybody being young, not having success and staying even keeled and not taking it into his defense. I think he’s handled that part amazing.”