Mariners' centerpiece in Brendan Donovan trade is already evolving for Cardinals

The Seattle Mariners traded two MLB Pipeline top-100 prospects over the winter, and both were expendable. Harry Ford was only ever going to back up Cal Raleigh, and Jurrangelo Cijntje was the club's third-best pitching prospect.

In fact, rumors of the Mariners being willing to trade Cijntje started percolating about a month before he actually went to the St. Louis Cardinals. The return was Brendan Donovan, who is doing everything in his power this spring to ensure Seattle won't get buyer's remorse.

Meanwhile, the Cardinals have pretty much committed to the same path the Mariners were going to take with Cijntje. He was drafted as a switch-pitcher in 2024, but it's clear by now that his right arm is going to be his money-maker as a pro.

And even if that's going to work, the 22-year-old needs to evolve.

Jurrangelo Cijntje already seems to be switching things up at Cardinals camp

If anyone in Seattle is curious as to how that effort is going for Cijntje, he recently made his spring training debut against the New York Mets on Wednesday. He logged two scoreless innings, and a couple things stand out.

For starters, he only averaged 95.7 mph on his fastball, with a high of 96.9 mph. We say "only" because he's gotten as high as 99 mph from the right side in the past. If the idea is to trade velocity for better fastball command, misses to his arm side and below the zone suggest there's work to do there.

He did, however, pick up a couple swinging strikeouts on breaking balls. He did have harsh shadows in his favor, yet the specifics are liable to catch the attention of Mariners and Cardinals fans alike.

As per Thomas Nestico, Cijntje showed two distinct breaking balls: a slider and a sweeper. The two had similar velocity in the 83-ish mph range, and even similar vertical movement. Unsurprisingly, though, the sweeper had more horizontal movement.

While Cijntje did talk about developing a sweeper from the left side in 2025, this appears to be the first time he's been confirmed to be throwing a sweeper from the right side. Reports on his right-handed pitching still characterize his main righty breaking ball as a slider, with only Baseball America noting that it has "a bit more sweep" than the one he threw as a lefty.

There isn't any downside to Cijntje experimenting with two different breaking balls, if for no other reason than they allow him to give hitters different looks. But for righties, sliders and sweepers are more right-on-right weapons than right-on-left weapons.

It's lefties who present a bigger threat to Cijntje, as shown in his minor league splits from 2025:

• As RHP vs. RHB: .480 OPS
• As RHP vs. LHB: .845 OPS

What he really needs is a reliable changeup or splitter, or really anything with arm-side movement and enough speed differential to keep lefty hitters off his fastball.

One supposes we'll see how that goes. It's hard to make any predictions either way, and not just because Cijntje is still early in his journey as a righty-only pitcher. Chaim Bloom only just took over the Cardinals, so they don't really have an identity yet when it comes to player development.

It's far from time for the Mariners to have buyer's remorse, in other words. The team can just be happy it was able to get Donovan, and that neither Kade Anderson nor Ryan Sloan had to go to St. Louis to make it happen.