Who will be the first person called up from the minors this year?
For a team with as talented a farm system as the Mariners, it can be hard to predict what move they make first. More than likely, the first name to get called up will be replacing an injured person currently on the major-league roster, but let's assume this question is really asking who the first prospect to get called up purely based on merit will be.
I don't drink kombucha or other probiotics much so I'm not sure if it's very trustworthy at this time, but my gut wants to scream Tyler Locklear. His ability to play both corner infield positions is immensely valuable as it's arguably where Seattle's roster has the most uncertainty. Ty France has spent the offseason at Driveline, a facility that reinvented J.P. Crawford to be one of the best shortstops in MLB, but will that pay off? What if the many options the team has at third base still aren't good enough?
Locklear can fill in the gaps at both spots and has been exceptional this spring, posting a .968 OPS over 26 plate appearances. He hasn't received any fielding reps at third base thus far and really seems to focusing in on first base so he may only be targeting Ty France's job, but his stock has gone up quite a bit in this offseason regardless of where he'll finally end up.
I think that the other names that are slated to debut this year like Jonatan Clase and Ryan Bliss are more dependent on injury simply because the starting talent for those positions is already quite good. That being said, Jorge Polanco is known to miss significant time due to injuries so Bliss may get his call-up sooner than Clase.
I also imagine they will call up at least one reliever closer to the beginning of the year given that Matt Brash and Gregory Santos won't return until April at the earliest. I'm not sure if picking Ty Adcock is cheating given that he already pitched 15 ⅔ innings in 2023, but if not him then Taylor Dollard is probably the next best bet. He pitched to a 2.25 ERA in 2022 over 144 innings but was sidelined for most of 2023 after receiving surgery to repair his labrum.
While he's being trained as a starter, it's not totally uncommon for future starting pitchers to dip their toes in the major leagues coming out of the bullpen. Corbin Burnes did this and Reynaldo Lopez came in as a starter, got moved to the bullpen, and is now in Atlanta's rotation.