Trumbo, 29, had been the odd man out in the Diamondbacks outfield, with 24-year-old Ender Inciarte taking over the third starting spot in the outfield, alongside David Peralta and A.J. Pollock. With that in mind, Trumbo was a prime trade candidate.
Thus far this season, Trumbo has been hitting .259/.299/.506 (115 wRC+) with nine homers and 23 runs batted in over 184 plate appearances. The downside to Trumbo is that he does not walk a lot and strikes out a ton.
The Mariners' offense has been horrific this season, ranking 28th in the Major Leagues in runs scored before today's game when they only plated one against the Yankees and Masahiro Tanaka.
Seattle has a full outfield, so it looks as if Trumbo will be upgrading Logan Morrison, who has a 100 wRC+ and just a 0.2 fWAR this season. Trumbo, on the other hand, has been worth 0.5 fWAR. He does provide a power boost to the Mariners lineup.
The main piece that the Diamondbacks will be getting in return for Trumbo is catcher Welington Castillo, who will try to patch up the Arizona's shaky catching situation. The team is tied for the worst catching unit in baseball at just 0.8 wins above replacement.
Castillo has not done much this season. In fact, his offense has been some of the worst in baseball, but he has just 75 plate appearances, due to not having the starting catching job in neither Chicago with the Cubs or with the Mariners this season. Castillo was dealt from Chicago to the Mariners on May 19.
On the season, he is hitting a dismal .162/.213/.279 this season with one homer and seven runs driven in.
Vidal Nuno and Dominic Leone are the two other Major Leaguers moving in this deal. Nuno is an extra starting pitcher for Seattle, but he is nothing special. He can work out of the bullpen and can provide a spot start.
Dominic Leone is a hard throwing righty that pitched pretty well out of the Mariners bullpen last season, working to a 2.17 ERA. The results have not been the same this year, as his ERA has ballooned to 6.35.
Gabriel Guerrero is one other interesting moving piece in this deal. Guerrero, the nephew of Vladimir Guerrero, has shown some decent power in the lower-level minor leagues with Seattle, with the 21-year-old reaching Double-A for the first time this year.