Magill announced his retirement via his personal Twitter account Thursday.

The Mariners released Magill on Saturday.

Magill (shoulder) worked around three walks during a scoreless sixth inning in a Cactus League tie with the White Sox on Friday, a game that marked his spring debut.

Magill (shoulder) returned to Seattle on a minor-league contract Thursday, Corey Brock of The Athletic reports.

Magill (shoulder) became a free agent Thursday after refusing an outright assignment to Triple-A Tacoma.

Magill underwent surgery on his right shoulder Tuesday.

Magill was placed on the 10-day injured list with a right shoulder strain Friday.

Magill, who's fired seven scoreless innings across seven appearances thus far this season, has succeeded by taking a more aggressive approach and also incorporating more breaking pitches with effectiveness, Greg Johns of MLB.com reports. "I'm really happy for Matt," manager Scott Servais said. "He has two awesome breaking balls. He throws the curveball hard down, and the slider with it. We haven't seen the velocity we saw sometimes last year, but the command of his breaking balls and the late bite to it is really effective."

Magill, who fired a scoreless eighth inning during which he issued a walk in a loss to the Rockies on Saturday, has five scoreless appearances to open the season but no save chances.

Magill, who entered the season in line for save opportunities, worked the fifth inning in his 2020 debut Sunday against the Astros, firing a scoreless frame in which he allowed a hit and a walk while recording two strikeouts.