The Mariners have a new closer in Edwin Diaz and he's a potential superstar talent

Diaz is good and interesting and ... well, really good

The Mariners didn't make many moves prior to Monday's trade deadline, but they did make a noteworthy one hours later, removing Steve Cishek from the closer's role following another late loss.

Cishek yielded the go-ahead run to the Red Sox just a night after blowing a three-run save opportunity against the Cubs. His seasonal numbers -- mostly his 120 ERA+ and 3.88 strikeout-to-walk ratio -- belie the facts that he's allowed at least one run in five of his last 10 appearances, and that he's struggled throughout the season with keeping the ball inside the fences. For now, Cishek will try to get back on track in middle relief.

In Cishek's place, the Mariners will use Edwin Diaz. If you're unfamiliar with Diaz, then you haven't been paying attention. He's the 22-year-old who, in 25 innings this season, has struck out 49 batters -- or 45 percent of those he's faced. That's the highest strikeout percentage among pitchers with more than five innings thrown. Add in a 6.4 percent walk percentage, and Diaz is in elite company:

Pitcher IP SO% BB% Contact%
Diaz 25 45.0% 6.4% 62.9%
Dellin Betances 51.1 44.3% 7.4% 58.7%
Andrew Miller 45.2 44.3% 4.0% 61.4%
Shawn Kelley 38.1 39.5% 4.6% 67.4%
Kyle Barraclough 45 39.0% 15.9% 65.8%

In addition to exciting numbers, Diaz features an interesting story. He transitioned to the bullpen earlier this season while at Double-A, and subsequently skipped Triple-A to join the big-league fireman staff. Diaz has since rewarded the Mariners' faith in him, relying heavily upon his upper-90s fastball and slider. But this isn't your typical case of a youngster leaning on his natural talents and nothing else.

Rather, Diaz's slider is a recent innovation -- one borne from a grip tweak suggested by former teammate Joaquin Benoit. Diaz apparently started throwing the slider sometime in mid-to-late June -- or about a week or two into his big-league stay -- and while the exact date is unknown, we can gather this much: since July 1, batters have whiffed on nearly 70 percent of their swings against the pitch. That's an absurd rate.

The kicker is that Diaz looked like he would be effective before making the switch. Why wouldn't he have been? His fastball can touch 100 mph and evades bats like it's nothing. Yet the combination of Diaz's old heater and new slider have him looking like more than one of the best young relievers in baseball -- it has him looking like one of the best relievers period. Now he'll get the chance to earn bigger checks down the road by closing out games.

Here's hoping that when the time comes, Diaz remembers to buy Benoit a nice watch or some office supplies or something.

CBS Sports Staff

R.J. Anderson joined CBS Sports in 2016. He previously wrote for Baseball Prospectus, where he contributed to five of the New York Times bestselling annuals. His work has also appeared in Newsweek and... Full Bio

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