What is a Paul Sewald? The Answer may be the Mariners future Closer

Ben Ranieri
SEATTLE - JUNE 17: Paul Sewald #37 of the Seattle Mariners pitches during the game against the Tampa Bay Rays at T-Mobile Park on June 17, 2021 in Seattle, Washington. The Mariners defeated the Rays 6-5. (Photo by Rob Leiter/MLB Photos via Getty Images)
SEATTLE - JUNE 17: Paul Sewald #37 of the Seattle Mariners pitches during the game against the Tampa Bay Rays at T-Mobile Park on June 17, 2021 in Seattle, Washington. The Mariners defeated the Rays 6-5. (Photo by Rob Leiter/MLB Photos via Getty Images) /
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Paul Sewald had not posted an ERA below 4.55 in parts of four seasons with the New York Mets. Often forgotten and shuttled between Syracuse and New York, he was non tendered and left without a team following the shortened 2020 season. Enter the Mariners.

On January 8, 2021, Jerry Dipoto signed the funky throwing righty who had been just recently non-tendered by the New York Mets to a Minor League deal. Sewald had a rough Spring, posting a 7.94 ERA in 6 appearances.  Following Spring Training, he was demoted to Tacoma where he began the season.

However underlying data suggested this new and improved arsenal could be a deadly one. He posted a 19 K/9 rate, albeit in a small sample size, over the Spring and started to generate swings and misses on both fastball and slider.

It turns out that Mariners RP Paul Sewald is a strikeout machine.

In the 24.2 innings since his call-up on May 13 Sewald has been absolutely terrific. Currently, he boasts an ERA of 1.52, a WHIP of 1.01, and a K% of nearly 43%!! His K/9 ranks higher than that of Josh Hader, Devin Williams, and Craig Kimbrel, and is first among all relievers with 20 innings thrown. Out of absolutely nowhere, Sewald has been the high leverage choice of Mariners manager Scott Servais to dominate the middle of the order bats across the American League.

Sewald’s transformation has been anchored by a switch to a two-pitch mix. In previous years he had relied on an ineffective changeup to pair with his best pitch, his slider. In 2021 Sewald ditched the changeup, opting to throw more sliders instead.

Perhaps the biggest development has been his willingness to attack the zone with an upper-echelon fastball. While his fastball ranks in the 34th percentile in velocity, it has ticked up to the 84th percentile in spin rate per Baseball Savant. This is a near 20% increase since his days with the Mets, where his spin ranked in the 63rd and 74th percentile.

Attacking the top of the zone with a swing and miss fastball and dominating the zone with a filthy slider has found Paul Sewald a home in the Mariners bullpen. His improvements suggest that his performance is not only sustainable but extremely rare.

The 31-year-old Sewald stonewalled the Yankees again on Thursday afternoon in Seattle, striking out Brett Gardner in the top of the 8th inning and letting out a roar towards the Mariner bullpen. Whether or not Jerry Dipoto sees fit to keep Sewald around following the July 30 deadline remains to be seen. For now, however, it seems the Mariners have found one of the most dominant and unlikely bullpen forces in baseball.

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