Mills, who fired a scoreless two-thirds of an inning in a loss to the Rays on Friday, has posted a 1.59 ERA and 0.53 WHIP across 5.2 innings over his first four appearances.
The right-hander has been a pleasant surprise since being recalled from Triple-A Tacoma, where he'd been similarly impressive with a 1.93 ERA and 0.77 WHIP over six appearances. Mills has primarily been utilized in low-leverage scenarios thus far after posting a 9.95 ERA and 2.05 WHIP in 11 outings with the Mariners last season, but that could certainly change if he continues to impress.