Diaz, 22, has a 1.64 ERA and 16:1 K:BB ratio through 11 innings for Double-A Jackson.
The top prospect in the Seattle system, Diaz has been scorching to begin the season. He did fan 145 batters in 141.1 innings between High-A and Double-A last year, though also posted 4.57 ERA once he was promoted to the higher level. Still, he has a high-90's heater, improving off speed stuff and pretty stellar control. The Mariners have a rather poor farm system, but Diaz is the cream of the crop.