Seattle Mariners spring training camp is already underway, with pitchers and catchers reporting last week and live batting practices beginning. With a league-leading 17 Mariners slated to represent their respective countries at the upcoming World Baseball Classic, these early weeks will be key for management to assess the squad and non-squad invitees. The Mariners’ 26-man roster is mostly set, but there are battles to watch, prospects who could leap, and players looking to rebound after a disappointing 2025. This spring is less about filling holes and more about internal competition pushing the ceiling higher.

Narratives Abound as Mariners Begin Spring Training
Pitching Prospects

The hype around top-35 pitching prospects Kade Anderson and Ryan Sloan has grown quickly in the opening days of camp. Both looked sharp in their first bullpen sessions, and their stock has only risen after taking part in live batting practices against those preparing for the WBC.

Jun 21, 2025; Omaha, Neb, USA; LSU Tigers starting pitcher Kade Anderson (32) pitches against the Coastal Carolina Chanticleers during the ninth inning at Charles Schwab Field. Mandatory Credit: Dylan Widger-Imagn Images
Kade Anderson

Kade Anderson, drafted third overall in the 2025 MLB Draft and a College World Series winner, is not afraid of the spotlight, and that tenacity was evident again in live batting practice. After falling behind 3-0 against American League MVP runner-up Cal Raleigh, Ryan Divish of the Seattle Times reported that he pinpointed a fastball on the outer half to get Raleigh to pop up to shallow left. He then struck out his next three batters: Miles Mastrobuoni, Randy Arozarena, and Dominic Canzone.

Kade Anderson strikes outa Mastrobuoni, Arozarena and Canzone pic.twitter.com/Asczzu3Xdu

— Ryan Divish (@RyanDivish) February 14, 2026

Anderson has already put together a camp that makes the third overall pick and best college pitcher from last season look like a steal, and he will look to build on that momentum as spring training games begin later this month.

Ryan Sloan

Sloan has been similarly impressive. His 6-foot-5 frame already makes him look at home on the mound despite being only 20 years old. He topped out at 100 mph and regularly hit 99 mph during his bullpen session, putting himself in position to climb top 100 prospect lists as the season progresses. He also added impressive scalps to his spring résumé, battling deep into counts against Raleigh and Josh Naylor and striking out Arozarena.

After getting a swing and miss on a fastball at the top of the zone, Arozarena fouled off a couple of pitches before swinging through a sweeper with reportedly 20 inches of horizontal break, his bat ending up in the dirt near third base. These signs are extremely encouraging and help explain why the Mariners viewed Jurrangelo Cijntje as a tradable asset despite his own potential.

Ryan Sloan vs. Randy Arozarena. Wait for it. pic.twitter.com/4QNZP77xMs

— Ryan Divish (@RyanDivish) February 15, 2026

Spring training is always a time for prospect hype. These two must stay grounded, but they are in the right organization to maximise their abilities. Live batting practice in February is not indicative of how successful their careers will be, but the quality of stuff and the buzz around the two have been hard to ignore as the season progresses.

Back-Up Catcher Battle

Following the signing of Andrew Knizner, it looked as though the Mariners were content rolling with him as the backup catcher to Cal Raleigh. Since then, they have also added Jhonny Pereda, who featured in 30 games for the Minnesota Twins and Athletics in 2025.

Pereda provides good competition for Knizner and offers a different direction in terms of what he brings to the Mariners in 2026. Pereda offers the more intriguing offensive upside, finishing 2025 with a .325 OBP compared to Knizner’s .299, along with stronger batted-ball results (.354 BABIP to .239) and a slight edge in slugging (.333 to .299).

But it seems as though, with his experience and framing upside, it’s Knizner’s job to lose. This is particularly true as Pereda has one more option remaining to be used in the minors. However, with Knizner’s contract being only one year at $1 million, the Mariners could move on from that deal relatively quickly.

While being the backup to the best catcher in baseball might seem like a job with few opportunities, the Mariners would like to use Knizner at DH as much as possible to sustain his offensive output. Last year, that spot was taken up by Mitch Garver, who is no longer on the team. A lefty masher, his days behind the dish often coincided with games started by opposing left-handed pitchers. The Mariners have now handed that role to Rob Refsnyder, who may even lead off when the Mariners are facing a starting left-hander.

The Mariners now have options regarding what they want to prioritize with that roster spot: defensive stability or offensive upside. These two will want to make an immediate impact during spring training for the Mariners, especially with Raleigh expected to go deep in the WBC for Team USA.

Infield Jigsaw

The infield of the Seattle Mariners has been the talk of the offseason so far in the Pacific Northwest. Following the trade for Brendan Donovan from the St. Louis Cardinals, it has been widely discussed whether he will start at second or third base. According to early reporting from Mariners camp, Donovan has arrived early to begin working out at third. Daniel Kramer, reporting for MLB.com, shared clips of Donovan going through infield drills at third base after the workout with the rest of the infield unit had finished, with infield coach Perry Hill.

Brendan Donovan sticks around after a full infield workout to go through barehanded bunting drills from third base with Perry Hill. pic.twitter.com/OrHfFfD3fP

— Daniel Kramer (@DKramer_) February 14, 2026

This does not guarantee anything. Many assumed, due to his capability as a plus glove across multiple positions, that he would slot in at third. But playing for the Cardinals, it would never have been necessary for him to take regular reps there. So even with his versatility, it is necessary for him to get work in during spring training, as he will have to field there at some point during the season, even if Colt Emerson beats out Cole Young for the remaining infield spot.

It certainly seems like Young’s spot to lose. He has the big league experience and seniority and has reportedly returned in great shape after putting on weight over the offseason. Nonetheless, it will be a fascinating battle. Emerson has also started workouts strongly, and the front office has praised him all offseason.

The future may not fully arrive on Opening Day, but it is clearly knocking on the door for the Mariners at spring training in Peoria, Arizona.

 

Main Photo Credit: Jerome Miron-USA TODAY Sports