While trades always seem to be surprising in some way, this particular trade is significantly less so. The Mariners currently have two-fifths of their rotation on the disabled list (Felix Hernandez, Wade Miley) and reports of Taijuan Walker's lingering foot injury aren't particularly encouraging. Should Walker need time on the disabled list, the Mariners' top in-house options include Donn Roach and Cody Martin. Things could be better.
The acquisition of Lee gives the Mariners that much needed depth which has suddenly become so vital in the team's immediate future. Lee is a former top prospect in the Dodgers' system, ranked as high as the 45th-best prospect in all of baseball back in 2012 by MLB.