The 30 year old Montero was signed as to a minor league deal as a free agent by the Rangers in January, 2019. Montero was rehabbing from Tommy John surgery which cost him all of the 2018 season, and he was released by the New York Mets, the team he had spent his entire career with, in November, 2018.
Montero returned to the majors in the second half of 2019 and pitched well, putting up a 2.48 ERA and a 3.83 FIP in 29 innings over 22 games for Texas. He took over the closer role for the Rangers in 2020 and logged eight saves in 17 games, with a 4.08 ERA and a 3.70 FIP.
Montero has a 7.27 ERA in 40 games and 43.1 IP for the M’s this year, albeit with a 4.04 FIP. His strikeout rate is down to 7.7 K/9, however, compared to the 10.2 K/9 he had while with the Rangers, his walk rate is up, and his home run rate has almost doubled.
Montero was dealt to Seattle this past winter for Andres Mesa, an 18 year old infielder who is slashing .281/.425/.438 through 40 plate appearances in the Dominican Summer League, and Jose Corniell, a (barely) 18 year old righthanded pitcher who has allowed 15 runs in 11 innings in the ACL so far this year, but who has also struck out 15 batters and walked just three.