Cardinals' Changeup Specialist Must Add More Weapons to Arsenal in '27

Growth, as St. Louis Cardinals’ manager Oliver Marmol pointed out repeatedly over the final month of the 2026 season, can be measured in a variety of ways.

One way, of course, is the standings – an area where the Cardinals fell back a win from 2025 (78-84) to 2026 (77-85), one that was somewhat expected with the widespread youth on the roster and the club selling off veteran pitchers JoJo Romero and Dustin May for prospects at the MLB Trade Deadline.

Instead, the Cardinals tried to evaluate areas of growth in non-traditional ways in a non-traditional season in St. Louis.

Growth was having a defined core group of players – Alec Burleson, Jordan Walker, JJ Wetherholt, Ivan Herrera, Masyn Winn, Michael McGreevy, Kyle Leahy and Riley O’Brien – take major steps in their games and evolve into building blocks.

Growth was seeing Leo Bernal, Joshua Baez, Quinn Mathews, Cooper Hjerpe, Nathan Church and Luis Gastelum live up to the hype that followed them from the Minor Leagues and show signs they can be depended on going forward.

Growth was Andre Pallante and Gordon Graceffo shaking off the struggles of 2025 and showing the fortitude to change the trajectory of their careers.

Growth was even journeymen relievers Justin Bruihl and George Soriano pitching better than they ever have in their careers.

“This is a really young group, but there’s been a lot of progress with so many of these guys,” Marmol said. “You can go up and down the lineup and you see growth from so many of our guys. Then, go to the rotation and what McGreevy, Pallante and Leahy did this season, and the bullpen as well. Our staff has really enjoyed pouring into that group. They are hungry for information and they want to be coaches, so that’s made it a lot of fun.”

However, as president of baseball operation Chaim Bloom reminds, the Cardinals still have major gulfs between them and MLB’s top teams. The National League champion Brewers, after all, finished 26 games ahead of St. Louis and battered the Cards in 11 of 13 head-to-head meetings. Much more growth is needed for the Cards to better navigate the difference the rebuilding and contending.

With growth being the focus, let’s look back at the performances by individual players in the 2026 season and how they will figure into the Cards’ plans going forward in 2027 and beyond:

Player name: Luis Gastelum

Age: 25

How acquired: Signed to a Minor League contract as a free agent in April 26, 2023

2026 statistics: MLB – 34 games, 5-4, 4.42 ERA, 36 2/3 IP, one hold, 0 for 2 in save opportunities, 33 hits, 18 earned runs, six homers allowed, 44 strikeouts, 12 walks, .241 batting average allowed; Triple-A Memphis – 36 games, 7-1, 2.27 ERA, 43 2/3 IP, five holds, 3 for 5 in save opportunities, 26 hits, 11 earned runs, two homers allowed, 49 strikeouts, 17 walks, .172 batting average allowed

Key numbers: Gastelum’s changeup is an absolute game-changer and a devastating pitch for him. He threw it 37 percent of the time in 2026, and foes hit just .169 against that pitch. Incredibly, Gastelum piled up 32 of his 44 strikeouts with the changeup.   

Looking back to 2026: Promoted from Triple-A Memphis on July 8 following a strong run there where he went 7-1 with a 2.27 ERA over 36 games, Gastelum got a heavy taste of how different MLB hitters are in his first month of action. In his 10 outings, Gastelum surrendered four homers and was rocked to the tune of a 6.30 ERA. After learning how to better set up his changeup with his other pitches, Gastelum made tremendous improvements in August (4.20 ERA, one homer allowed, 24 strikeouts and four walks) and September (3.09 ERA, one homer allowed, 12 strikeouts and four walks).  

Looking forward to 2027: Gastelum showed the Cardinals that he definitely belongs at the big-league level, but he still has plenty of improving to do to evolve into a reliever they will trust in high-leverage innings. His changeup features 44.6 inches of vertical drop – 5.9 inches greater than comparable changeups. However, he must become more effective with his other pitches to keep hitters off the changeup. Foes batted .306 against his four-seam fastball and .360 against his sweeper – pitches that need improvement. In some respects, his splits against right-handed and left-handed hitters in 2026 didn’t add up. Lefties hit just .230 against him and they accounted for 26 of his strikeouts, but they also smashed five homers off Gastelum. Righties reached him for a .254 batting average, but they hit just one long ball off him.  

Denton’s analysis: Even though Gastelum’s average fastball sits at 93.9 mph, he knows how to keep baseballs off the barrel of the bat, for the most part. His average exit velocity allowed (86.8 mph) and hard-hit rate (30.9 percent) would rate in MLB’s top third among all pitchers, and his chase rate (33 percent) and whiff rate (34.7 percent) remain high because of the darting movement on his changeup. If the Gastelum can add some bulk and muscle to his rail-thin frame, he could potentially add more horsepower to his fastball – something that should make his changeup even more effective. Gastelum already has the out pitch that so many relievers spend years searching for, but now he must work back from that and improve his other offerings to make himself a more complete pitcher.