The 25-year-old Guenther is now in position to make his Major League debut. A seventh-round pick out of Notre Dame in the 2017 draft, Guenther isn’t ranked by either Baseball America or MLB Pipeline as one of Miami’s top 30 prospects, but the lefty has earned his promotion with some strong numbers. Since becoming a full-time relief pitcher in 2019, Guenther has greatly increased his strikeout totals, with a 34% K rate over 40 1/3 combined innings at Double-A and Triple-A ball this season.
2021 marked the first time Guenther had pitched beyond the A-ball level, and while he performed well at Double-A, his 4.76 ERA over 22 2/3 Triple-A frames indicates some growing pains. Still, much of that damage was done over two calamitous outings on July 6 and 9, as Guenther allowed nine runs over 1 2/3 total innings.
While Guenther will get his first taste of the majors, Diaz heads back to Triple-A after another brief stint with the Marlins. Diaz has only a .496 OPS over 73 career plate appearances with Miami, but the 24-year-old has already displayed a lot of power potential down on the farm, albeit without much plate discipline.