The Tampa Bay Rays have made a habit of finding pitchers and turning them into successful reclamation projects under the tutelage of pitching coaching Kyle Snyder.
In a Tampa Bay season full of injuries to pitchers, Stephenson has emerged as the best turnaround story on the club.
Stephenson, 30, struggled with the Pittsburgh Pirates this season, going 0-3 with a 5.14 ERA in 18 appearances, but Snyder felt Stephenson's outstanding slider would work well with the Rays.
On June 2, the organization acquired him in exchange for shortstop prospect Alika Williams.
"We knew the (slider) had improved," Snyder said. "I think it's probably outperforming our own internal numbers."
It certainly has.
Since changing teams, Stephenson ranks among the major league leaders in whiff rate, the percentage of swing and misses divided by swings. His figure is just over 50 percent with Tampa Bay.
Through 31 2/3 innings over 34 appearances under Snyder, the 2011 first-round pick has allowed only 14 hits and eight walks while striking out 49 — 13.9 K's per nine innings.
Stephenson is 2-1 with a 2.56 ERA and a 0.69 WHIP for the Rays after throwing a perfect inning on Wednesday in the Rays' 3-1 victory over the Boston Red Sox. Batters hitting just .132 against the right-hander since he changed teams.
"It's been pretty eye-catching just to see the number of swings and misses that are occurring on that particular pitch," Snyder added. "The slider's performance has really been incredible."
Seattle (78-61), which sits in the second American League wild-card position behind Tampa Bay, went 21-6 last month (.777) and is 40-19 (.678) since the start of July. The Mariners sit one game behind the Houston Astros (80-61) in the AL West.
Despite the strong performances, Seattle is just 2-4 to begin its 10-game road trip. The Mariners avoided being swept in Cincinnati by beating the Reds 8-4 on Wednesday before flying to Florida.
J.P. Crawford, Cal Raleigh and Mike Ford homered to back the nine-strikeout pitching of Logan Gilbert as the Mariners fortified their postseason push.
Seattle manager Scott Servais will send out Luis Castillo (11-7, 3.19 ERA) in the series opener against the Rays.
Opponents are batting .214 against Castillo, which leads the AL among qualified starters. He is 0-0 with a 3.46 ERA in two career starts against the Rays. Castillo got a no-decision vs. Tampa Bay on July 2 after yielding six runs, four earned in six innings.
"You can feel the positivity and the good vibes here," Castillo said of his team's strong August run. "It's a team that just wants to go out there and win."
Zack Littell (3-4, 4.69 ERA) will make the start for Tampa Bay after allowing exactly four runs in each of his past three outings. In his lone career appearance against the Mariners, he tossed a perfect inning of relief with two strikeouts at Seattle on July 2.
—Field Level Media