SoDo Mojo’s Top 40 Seattle Mariners Prospects: #4

The one that got away, then eventually made his way back around.

Coming in at the fourth spot of our re-rank of the Mariners’ farm system is Justin Dunn, a 23-year-old hard-throwing righty out of Boston College. Back in 2016, the Mariners were planning on drafting Dunn with the 11th overall pick in that year’s MLB amateur draft, though Kyle Lewis unexpectedly fell to them and, well, it was a no-brainer to take the Golden Spikes Award winner.

Dunn wound up going eight spots later to the Mets, where he would struggle for the first full year of his professional career, but later figured things out in a dominant 2018 season from High-A ball to Double-A. Now, Dunn has found his way back to Seattle after the Mariners acquired him in the famous (or infamous, depending on who you root for) Robinson Canó/Edwin Díaz trade with the Mets last December. And, as the baseball gods have willed it, both Lewis and Dunn made their Major League debuts just days apart from one another for the Mariners last week.

Prior to his debut, Dunn pitched the entire season for a really good Double-A Arkansas squad. In 131.2 innings thrown, Dunn posted a 3.43 FIP with a 10.80 K/9 and 2.67 BB/9. His 158 strikeouts landed him atop the Texas League leaderboard and second overall in the entire Double-A circuit for the season. He was also selected for this year’s Futures Game back in July, where he threw a scoreless inning that included a strikeout of top Padres prospect Taylor Trammell.

For Dunn to be successful as a Major League starter, he, like pretty much every other young pitching prospect, must find a viable tertiary pitch with a changeup that’s still very much a work-in-progress. Right now, he boasts a really good fastball that sits in the mid 90s, but struggles to command it at times. His slider has also flashed plus some outings, but it’s definitely teetered in consistency.

When Dunn has worked out of the bullpen in the past, that mid 90s velocity suddenly jumps up into the high 90s and even sniffs triple digits. Pair that with the slider when it’s on and Dunn, in theory, becomes practically unhittable.

A move to the bullpen will likely be the Mariners’ last resort. They’re going to give Dunn any and every opportunity to become a centerpiece in their rotation. But at worst, he’s a high-leverage reliever in a good Major League bullpen. That’s nothing to scoff at.