The Seattle Mariners have been surprising quite a few people so far this season. Entering action on July 4th, they’re just 0.5 games behind the first-place Houston Astros in the American League West off the strength of a 55-31 record.

How have they been able to manage this, especially with second baseman Robinson Cano currently serving a suspension? Well, we’ve previously touched on their ability to win one-run games, which certainly helps. One of the keys to that level of success in close contests, though, is a strong bullpen.

According to fWAR, the Mariners have a top-10 bullpen (3.2 fWAR). But it’s basically because of closer Edwin Diaz, who has been worth 2.2 fWAR on his own through 45 innings of work. That’s already a single-season career-high mark for him.

The hard-throwing right-hander collected another save on Tuesday night. It was the 33rd time he’s shut the door on a Seattle victory, which leads the league. And if you think he’s been racking up saves at a very high rate, you’d be right.

He’ll only need one more save to match his 2017 total. Something tells me that’ll happen pretty soon.

Diaz has been a useful reliever since debuting in 2016, but he’s clearly rebounded after taking a step back last season. Here’s how his ERA, SIERA, strikeout rate (K%), walk rate (BB%), and homers allowed per nine innings (HR/9) stack up during his short MLB career.

This bounce-back has been aided by some drastic changes in his batted-ball profile, too.

After watching hitters register a pull rate north of 40.0% in 2016 and 2017, that number is down to 28.9% so far this season. He also boasts a soft-hit rate (26.5%) that’s higher than his hard-hit rate (21.7%), both of which are on track to be career-best marks.

Diaz is a fastball-slider pitcher, and there’s been a clear change in pitch mix (along with pitch quality) in 2018. After throwing his slider 32.3% of the time in 2016 and at a 31.5% rate in 2017, it’s all the way up to 39.0% at the moment.

The value of this pitch on a per-100-pitch basis has improved from 1.79 last year to 2.59 so far this year, according to FanGraphs. It’s easily the most effective pitch in his arsenal — hitters have produced a 55.6% strikeout rate, 28.1% swinging-strike rate, and a 5 wRC+ against it.

If the Mariners plan to keep pace with the Astros — and at the very least, hold on to one of the AL wild-card spots — they’ll need Diaz to continue locking down the ninth inning in close games like he has over the past few months.

About Matt Musico



Matt Musico currently manages Chin Music Baseball and contributes to The Sports Daily. His past work has been featured at numberFire, Yahoo! Sports and Bleacher Report. He’s also written a book about how to become a sports blogger. You can sign up for his email newsletter here.

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