Mariners: The Crucible of Edwin Diaz

Mariners closer Edwin Diaz has been much worse so far in 2017 than 2016 across the board. Advanced stats suggest hitters have adjusted to the fireballer. What should be done with Diaz now?

Mariners closer Edwin Diaz blew three saves last season. He became the team’s closer after Steve Cishek struggled with consistency and health. The switch to Diaz was advantageous. He saved 18 games, struck out 88 batters in 51.2 innings, and seemed to be the closer of the future for the Mariners.

But people forget that Diaz is only 23 years old and a former starter in double-A before he was thrust into high-leverage relief situations for Mariners manager Scott Servais in 2016. It’s very difficult to fool major league hitters for long, and in 2017, the league has appeared to adjust to him, and Diaz’s pitches haven’t been nearly as effective as last season.

First, some statistical breakdowns:

Diaz last year had a 2.79 ERA and a 2.04 FIP. He allowed five home runs in his 49 games, and his fastball, while averaging over 97 MPH, was actually 1.5 runs below average in value, but his slider was nasty–providing 9.9 runs over the average in value, per Fangraphs. He also kept the ball on the ground. His ground ball percentage (GB%) was 46.8%. Only 30.6% of his opponents hit his pitches in the air, and only 14.7% of those fly balls left the yard.

Diaz saved games for the Mariners last season by striking out so many batters that his FIP was three-quarters of a run below his official ERA and by keeping his batted balls in the park and on the ground for the most part.

This year, it’s been an about-face:

3.44 ERA; 4.65 FIP; 8 HRs, -0.8 Fastball value; 2.5 Slider value; 40.9 GB%; 47.7% FB%; 19.0% HR/FB ratio.

Diaz has managed to halve his line drive percentage from last year in 2017, but hitters are lifting the ball in the air more and those fly balls are flying away at a greater rate. Diaz’ walk rate has risen this year, as well, so those home runs have hurt the Mariners more.

Hitters could simply be sitting on Diaz’s hard-but-straight fastball and spitting on that nasty slider, which itself hasn’t been the pitch it was last year.

What Should the Mariners do with Diaz?

There are a few schools of thought about what to do with Diaz this year and in the future.

When Diaz is ‘on,’ he’s almost unhittable:

Last night he blanked the White Sox in the ninth to help the Mariners to a 4-2 win and looked like his 2016 self. He seemed more willing to go to his money-pitch, the slider, to get the save.

Perhaps he’ll settle down for the rest of the season and head into 2018 the unquestioned closer for the Mariners.

But if he continues to struggle down the stretch and the Mariners fall further from playoff contention, Servais and Mariners General Manager Jerry Dipoto will have decisions to make.

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Maybe Diaz was rushed, a la Mike Zunino, to the big leagues to fill an immediate need. He was electric last season but this season the league knows him and knows how to hit him. Maybe he’ll benefit from dominating AAA hitters in Tacoma for the rest of 2017 instead of wavering on the mound for the Mariners.

Perhaps Dipoto, Servais, and Director of Player Development Andy McKay will take a radical approach and convert Diaz back into the promising young starter he was envisioned as before his rapid call-up last season. As it stands, Diaz essentially has two pitches, not enough to be a Major League starter. But at only 23 years old, Diaz could learn one or two more pitches and become effective and possibly dominant. That will be years down the road, and he’ll have to figure out how to put more movement on his fastball, but it’s possible for a player at his stage of development.

Next: Mariners Second Half Outlook and Priorities

The Mariners are in dangerous territory. They have a will-they, won’t-they vibe about them to start the second half. They’re a couple players from seriously contending for a playoff spot in 2017, and they could still use young players in their farm system for 2018 and beyond. The last thing I want to see is the Mariners squandering Diaz’s talent the way did Brandon Morrow, another hot-shot young starter-turned reliever.