Diaz will replace Steve Cishek as the Mariners' closer, Ryan Divish of the Seattle Times reports.
Cishek has struggled trying to close out games lately, so manager Scott Servais decided it was time for a change at the back end of the bullpen and will go with Diaz next time the Mariners need to lock up a win. Diaz has appeared in just 24 big-league games, but owns an eye-popping 17.6 K/9 rate and has allowed just five earned runs over that span, so he could close the rest of the way if he proves the ninth-inning role isn't too big for him.