4 prospects the Cardinals must add to their 40-man roster to protect from Rule 5 draft

With the St. Louis Cardinals prioritizing the future this offseason, there is even more intrigue than usual surrounding who the club will protect ahead of tonight's Rule 5 protection deadline at 6pm EST, especially with the number of names for whom you could make an argument.

The Cardinals got to work earlier this offseason, clearing 40-man roster space, as they currently have three open spots after passing various players through waivers and adding OF Bryan Torres to the 40-man roster.

There are still names out there that I expect the Cardinals to add to their 40-man roster ahead of tonight's deadline to ensure they will remain with the organization in 2026, so here are my predictions for who they will be adding or making space for this evening.

LHP Brycen Mautz

After being selected by the Cardinals in the second round of the 2022 MLB Draft, Brycen Mautz had a solid debut season in 2023, followed by big-time struggles in 2024, making his 2025 campaign a major milestone when it came to standing with the organization.

Mautz responded with a big year in 2025, posting a 2.98 ERA in 25 starts for their Double-A affiliate, striking out 134 batters in 114.2 innings of work and holding opposing hitters to just a .219 average, easily the best ratios of his career to date.

While Mautz isn't a big-time pitching prospect, he has certainly shown enough for the Cardinals to believe he could have a future as a big league starter or valuable left-handed reliever. I expect him to be one of the names they add to their 40-man roster this evening for that very reason.

While the Cardinals' pitching prospect pool has dramatically improved recently, I don't really think they are in a position to let someone like Mautz be subject to the Rule 5 draft later this winter. Now, the Cardinals are running into a bit of a sticky situation when it comes to how many MiLB arms they will have on their 40-man roster who are either hurt or haven't made an MLB Debut, but that's a problem to be managed. Maybe they think he'd be safe from the draft, but I wouldn't take any chances.

OF Joshua Baez

While I wouldn't be shocked to see Mautz not get the 40-man roster addition, I have zero doubt in my mind that rising prospect Joshua Baez will be added today.

Baez, who the Cardinals selected in the second round of the 2021 MLB Draft out of high school, really struggled in his minor league career prior to 2025 and was even left off many publications' top 30 prospects lists for the organization. But after a huge year at the plate, Baez is now forcing himself onto many top 100 prospect lists in baseball.

In 117 games this year between High-A Peoria and Double-A Springfield, Baez slashed .287/.384/.500 with 20 home runs and 79 RBI to go along with 54 stolen bases. Baez actually spent most of the year in Double-A, and his power took a jump at that level.

Baez's horrible swing and miss rate was holding him back big time in his development, but he cut down on his strikeouts in a significant way in 2025. In 2024, he struck out 114 times in 277 at-bats between Low-A and High-A, but this year, he only struck out 103 times in 418 at-bats against better pitching.

Baez has incredible 65-grade power according to Baseball America's 2026 preseason ranking, to go along with plus speed and arm tools. His now above-average hit tool grade means Baez has the upside to become a really impactful outfielder in the future who could slug for over 30 home runs and swipe 30 bases in a given year. That's hard to find in today's game!

The Cardinals' outfield production is not in a good place right now, and they desperately need power potential throughout their system, so there is no shot that. Baez won't be on their 40-man roster before the deadline.

While JJ Wetherholt and Rainiel Rodriguez rightfully lead the way among Cardinals' position player prospects right now, Baez made a huge splash this year and could quickly see his name thrown into even higher company if he repeats that success in Triple-A in 2026, and could be knocking on the door of St. Louis by the end of the season.

C Leonardo Bernal

The Cardinals have incredible catching depth in their system right now. At the Major League level, Ivan Herrera, Pedro Pages, and Yohel Pozo led the way for most of the 2025 season. Prospect Jimmy Crooks made his debut this year, and Rodriguez is one of the top prospects in the sport. But don't for a moment forget about Leonardo Bernal.

Bernal is the most all-around prospect of the Cardinals' catchers at this moment, boasting a really intriguing bat while winning the minor league Gold Glove for his performance behind the plate this year.

While his numbers at the plate were not flashy in 2025, it's important to remember that he was a 21-year-old in Double-A and playing as the primary catcher. Even with being younger than most of his peers at that level, Bernal slashed .247/.332/.394 with 13 home runs and 70 RBI in 396 plate appearances. There is a ton to like about Bernal, and you'd have to think that he has a bright future ahead of him.

As a switch-hitter, Bernal boasts an average hit tool and power at the plate who does more of his damage against left-handed pitchers. As he continues to develop physically and mature as a hitter at the plate, he could be even more impactful than that. Pair that with some great defense behind the plate, especially when it comes to managing stolen bases, and you've got a really intriguing player on your hands.

While the Cardinals will have to figure out what to do with their catching depth over time, Bernal is too talented not to add to their 40-man roster today. I wouldn't be surprised to see him traded this offseason in an opportunistic deal, but there is no way they would allow him to be grabbed by another organization for free. I wouldn't be surprised at all to see Pozo non-tendered or put through waivers to clear space.

LHP Cooper Hjerpe

Last but certainly not least, Cooper Hjerpe is the name that I fear the Cardinals may leave off of their 40-man roster this evening, but I really do believe he should be among the names added.

Hjerpe, the Cardinals' first-round pick back in 2022, has been dynamite on the mound for them since they drafted him, but the problem is he's barely pitched for them. Since being drafted, Hjerpe has pitched in just 25 games, posting a 3.38 ERA with 127 strikeouts in 93.1 innings of work.

Hjerpe had an awesome 2024 campaign that saw him start 15 games, striking out 76 batters in 52.1 innings with a 3.27 ERA between High-A and Double-A, and opposing hitters have a sub-.200 batting average off him for their career. Hjerpe doesn't blow you away with velocity, but his funky delivery and release angle allow him to attack hitters with great deception, and he's got some of the best strikeout stuff in the Cardinals' system.

Unfortunately, on top of the various injuries Hjerpe has experienced in his career thus far, he's currently rehabbing from Tommy John surgery and isn't expected to be back until sometime into the 2026 season. As I stated earlier, the Cardinals already have some rehabbing arms on their 40-man roster in Tekoah Roby, Tink Hence, and Sem Robberse, so the club may not want to have another arm taking up a spot like that.

But man, Hjerpe's stuff is just too good to give up on already. I still believe he has a bright future as a starter, but even if he can't stay healthy enough to do that, he could become a very valuable reliever going forward. Heck, even in 2026, I could see the Cardinals using him in that role to make the most of his 40-man spot and to develop him against high-level hitters while not wasting bullets in the minor leagues.

We are about to find out a lot about how Bloom's regime sees a player like Hjerpe. While his injury may cause other organizations to back off of him, I have a strong feeling that Hjerpe would be a top target of organizations that develop pitching well.