Mariners’ Diaz working on a new sweetener for his arsenal

Think hard Sugar was tough enough on a hitter’s diet? Just wait. Mariners closer Edwin Diaz is adding an extra sweetener to his pitching repertoire.

"I’m working on a change-up," Diaz revealed. "I want to throw change-ups this year. It’s going pretty good. I’ve been throwing it in the bullpen, and (pitching coach) Mel (Stottlemyre Jr.) likes it."

Think about that a moment.

A year ago, Diaz was a Double-A starter armed with a fastball that sat comfortably in the mid-90s. The Mariners saw that and, by May, shifted him to the bullpen in hopes of fast-tracking a much-needed power reliever to the big leagues.

Diaz made that jump in early June and, soon thereafter, tried a new grip on his slider at…