Justin Dunn came to Seattle in the Robinson Cano/Edwin Diaz/Jarred Kelenic trade. At the time Dunn looked like he could be the centerpiece of the return that the Mariners got, as he was the highest-ranked pitching prospect in the Mets system and was more MLB ready than Kelenic. However, Kelenic has totally taken that from Dunn as he is now a top ten prospect for all of the MLB.
Dunn has performed well so far in his major league career. In two shortened seasons due to the COVID pandemic as well as making his debut in September of 2019, Dunn has a 4.13 ERA in 14 games started and had two 6 inning shutouts in August of this year.
The problem for Dunn, and the reason he could be on the trade block, is when you get deeper into the analytics it’s not pretty. He has a horrible Baseball Savant page that has his best statistic as xBA, where he is only in the 44th percentile compared to other MLB pitchers. Dunn also has a career 6.44 FIP, which is well over his ERA. Another reason he could be on the block is the depth of pitching prospects the Mariners have, which could force Dunn into a bullpen role if he stays with Seattle.