Down on the Farm: Mariners Top Prospect Notes

Colt Emerson’s Huge Second Half

I put out a piece back in August highlighting Colt Emerson‘s swing adjustments that made in mid-June and the spectacular results that followed, catapulting him to No. 5 overall on Just Baseball’s Top 100 prospect list. In his final 75 games, Emerson slashed .315/.410/.521, cut his groundball rate by nearly 20% and finished the year with success in Triple-A.

On top of the mechanical adjustment, Toole keyed in on a approach shift in the box that helped Emerson produce in the second half of the season.

“The biggest change in the conversations with him is like, ‘man, you’ve got juice, you’ve got power’,” Toole said. Take your shots early and try to do some damage rather than just trying to shoot the ball through the infield.”

Emerson’s desire and ability to do damage in the air was plenty evident in those final 75 games. While his Hard Hit rate was identical at 43%, his average launch angle on batted balls 95 MPH and above jumped from 3 degrees to 12 degrees.

The desire to elevate more consistently and slug did not come at the expense of Emerson’s contact skills, cutting his strikeout rate by 2% in those final 75 games. In that span, he hit .330 against left-handed pitching with a .928 OPS.

If you ask Toole, the offensive side sprint through the finish line wasn’t even Emerson’s most significant gain.

“[Emerson’s] biggest improvements last year were the steps forward in the defense. Just the range, the ability — obviously he battled some injuries the year before, so just being fully healthy helped him a lot,” Toole said. “We knew coming in that he was a good defender and he just showed last year what he was really capable of doing.”

Emerson’s defensive improvements paired with the improved quality of contact combined to make him a top five prospect and now have the 20-year-old knocking on the door of the big leagues.

With the presence of JP Crawford at shortstop, Emerson’s first big league taste could theoretically come at third base with the Donovan moving to the outfield, highlighting why the former Cardinal was such a great fit for the Mariners in the first place.

Toole highlighted Emerson’s arm strength and accuracy as a component of his game that has consistently improved, making the third base fit even more clear before the eventual shift over to shortstop. Through Emerson’s first seven spring training games, he has made three starts at the hot corner.

“Five tools. He can do everything you want, along with the makeup and the stuff off of the field which is great,” Toole said.

Michael Arroyo’s Defensive Experiment

There’s no secret that Michael Arroyo‘s bat leads the way and while he has improved enough defensively at second base to get by. Given the infield talent the Mariners already have and Arroyo already being at the upper levels, the goal was to potentially give Arroyo more avenues to playing time at the highest level.

“He’s sneaky athletic, obviously really strong stocky build but can run a little bit, will surprise you on the bases. There definitely is an athlete in there,” Toole said.

The Mariners got Arroyo’s feet wet with the outfield while playing in the Colombian Winter League and he has taken reps at both third base and the outfield during camp. In preparation for the WBC, where Arroyo will play second base for Colombia, he has seen all of his spring training game reps at his usual position.

Some early reporting implied that Arroyo’s reps in the outfield were indicative of a positional change, but based on my conversation with Toole, it sounds more like the Mariners trying to open the door for other possibilities if the 21-year-old mashes his way into a situation where the team feels like he can help them win games in Seattle.

“My guess is likely a majority of reps are at second base,” Toole said. “Obviously things can change, but going into the season, just planning on splitting time between second base and then one of third base or left field depending on roster makeup, what level he is at and things like that.”

His arm strength may be stretched a bit thin for third base and his at least average speed underway could likely help him get by in left field more successfully than the left side of the infield.

Ultimately, if Arroyo reaches his offensive ceiling, the Mariners will find a spot for him one way or another in the lineup. Arroyo split his age-20 season between High- and Double-A where he posted a combined 139 wRC+, launching 17 homers, while getting on base at a .401 clip.

Arroyo has frame-defying pop, with a short-levered 5-foot-7 build that produced 43 extra-base hits, an average exit velocity of 89.5 MPH and a max of 111 MPH. That said, his ability to get on base and wear pitchers out in the box stands out as a clear strength.

“There’s just not a lot of room for pitchers to work with and I think that’s the thing that’s really exciting about him — there’s just so many different ways he can beat you,” Toole said. “He’s not afraid to get hit by the pitch. He’s not afraid to pull it if you bring it in. He’s not afraid to go the other way if you throw it away.”

Seven of Arroyo’s 2025 homers left the yard to the pull side, two to dead-center and the remaining eight homers ranged from right-center to straight away. He crowds the plate with a tight strike zone and leverages it with patience that resulted in a chase rate below 20%.

“ As he continues to learn himself as a hitter, what pitches he can do damage with, what pitches he can’t. How that affects his plan and approach and those types of things. There might not be a tougher out in the org,” Toole said.

Teddy McGraw Shifting to a Bullpen Role

After undergoing Tommy John surgery in high school, Teddy McGraw had first-round helium heading into his junior year. The right-hander unfortunately had to undergo his second Tommy John in January, but the Mariners still took him in the third round, signing him to a below-slot $600,000 bonus.

McGraw’s 2024 season was limited to just 8 2/3 innings due to an elbow flexor issue, delaying his start to the 2025 season as well. Though his workload was heavily monitored upon his return, never throwing more than three innings in an outing, 13 of his 15 appearances were starts. Including his postseason start, McGraw tossed 31 innings last year, pitching to a 3.19 ERA while posting an impressive 20.5% K-BB rate.

In an effort to preserve his health, the Mariners are transitioning McGraw into a relief role in 2026 where he will pitch in one-to-two inning spurts. The team came away encouraged by what they saw from McGraw last season with a clear big league reliever’s skill set if healthy.

McGraw’s fastball sat in the mid 90s last season, but his slider looks like a potential wipeout pitch, flirting with 3,000 RPM and averaging more than 17 inches of horizontal break with seven inches of vertical break. Unsurprisingly, opponents posted a 46% whiff rate against the pitch with a .386 OPS.

“His ability to spin the ball and what he can do with the breaking ball is second to none,” Toole said. “[McGraw] is a guy who has that kind of stuff can definitely move quick if things happen.”

Grant Knipp’s Two Way Dream is Still Alive

The Mariners are going to continue to pursue a two-way path with 2024 sixth rounder Grant Knipp. A catcher at Campbell who hit .402 while launching 19 homers in 29 games at Campbell in his junior season, Knipp also made a few appearances on the mound where his loud stuff stood out.

Knipp has yet to make his pro debut, missing the 2025 season after undergoing Tommy John. He will no longer catch, but the Mariners are still focused on keeping the bat in his hands for now.

 ”The plan for us is to continue to build him back up as a pitcher, get him some swings, and try to find a way to get him some DH at-bats while figuring out what it looks like for him on the mounds,” Toole said.

Early showings on the backfields before going down with the elbow injury in the spring only added to the excitement that the Mariners have about what Knipp can do at the plate and on the mound. His fastball touched 98 MPH in his limited 2024 regular-season action with a curveball that flashed above average, but unless he returns from the long layoff with a more diverse pitch mix, Knipp likely projects as a reliever.

It’s probably far-fetched that the 24-year-old prospect sticks with both hitting and pitching through the minor leagues and carries it into a big league debut, but the idea of a relief arm who could be a power bat off of the bench is a fun way to squeeze out every drop of a 26-man roster.

Under-the-Radar Names

• 2025 16th rounder Casey Hintz started his career at the University of Arizona as a two-way player before shifting his focus to the mound. It’s a funky side-arm delivery that he is still learning to harness, but the slider flashed above average and Toole said the stuff has taken a step forward this spring.

• 2025 6th rounder Lucas Kelly shares a lot of similarities to Hintz aside from the fact that he was a product of Arizona State. Kelly also entered college as a two-way player (you think the Mariners have a type?) and has limited pitching experience having only thrown 26 2/3 innings in his professional career. Kelly also throws from a sidearm delivery, but has more on his fastball, averaging 95 MPH between college and his pro debut with Toole believing the 22-year-old has room for even more velocity. Improved fastball quality would go a long way considering Kelly threw the pitch 80% of the time in 2025.

• Nick Becker is not necessarily an under-the-radar prospect given the fact that he was taken in the second round of last year’s draft, but in a system with the talent that the Mariners have and the limited exposure the 19-year-old has had in the early going of his pro career, he’s still a name that Toole believes is worthy of more attention.
  
  “He’s really wiry, big, strong, physical. You can see why our scouts loved him so much with just his athleticism and how he moves,” Toole said.
  
  Toole acknowledged that the teenage shortstop will need to clean up the swing and miss some, but the power potential combined with his athleticism at shortstop make Becker easy to dream on. The makeup only adds to that excitement for Toole as well.
  
  “He’s a confident kid. In meetings he’s not afraid to throw an answer out there. Not afraid to feel uncomfortable in front of the group,” Toole said. “Just competes, great teammate, fits in really well with the group.”