Seattle Mariners

Rookie Justus Sheffield improving efficiency, developing changeup in this stint with Mariners

Four starts into his big-league career, rookie starter Justus Sheffield is far from a finished product, but the Seattle Mariners are getting an early look at how effective the 23-year-old’s three-pitch arsenal could be for years to come.

“The confidence is growing,” Mariners manager Scott Servais said of Sheffield, who has allowed just one run in his past two starts, spanning 11 innings. “You can see him making pitches and slowing things down when he needs to. I just think he’s under control.

“He put a lot of pressure on himself, certainly, when he was here early (for one game in April), and in Triple-A. He’s relaxed (now). He’s getting back to doing what he’s doing, and trusts his ability at this level. And, it’s great he’s getting the results right now, too.”

Sheffield’s efficiency has steadily improved since in the four starts since his promotion from Double-A Arkansas — where he spent the majority of his first year with Seattle’s organization after arriving from New York in the James Paxton trade last offseason — at the end of August.

He averaged 21.5 pitches per inning in his first start on Aug. 23 against Toronto, but had pared that number down to 15.2 in his most recent start against the Reds last Tuesday.

And, he’s been effective for longer in each outing. Sheffield lasted just four innings against the Blue Jays, and managed just 4 1/3 against the Yankees five days later, but tossed five in Chicago against the Cubs during the last road trip, and a career-high six frames against Cincinnati.

His two most recent starts have undoubtedly been his best, though he’s still searching for his first career win.

He didn’t allow a run against the Cubs, yielding five hits and two walks while striking out a career-high seven on 91 pitches. And, he gave up just one run against the Reds on seven hits and three walks, while striking out four, again on 91 pitches.

“I feel good,” Sheffield said following his start against the Reds. “I’ve just got to keep working, keep building off every start. That’s what I’m looking forward to doing.”

As he’s moved along this last month, and gained familiarity, the finish on his pitches has been more apparent. His fastball has averaged around 93 mph, and against Cincinnati, had enough sink for him force a handful of ground balls that aided the Mariners in turning four double plays.

“The movement on his fastball is very unique,” Servais said. “It’s very late. Sometimes it’s darting down, sometimes it’s cutting in on the right-handers. It’s got late life to it. And then the slider off of those really plays.”

Sheffield’s slider, arguably his most effective wipeout pitch in the big leagues to this point, has played at about 84 mph. He’s produced 34 swinging strikes on his slider in his four starts — including 14 against the Cubs, when he logged an impressive 21 swinging strikes total in five innings — and has registered 20 of his 22 strikeouts this season with it.

But, as much as those two pitches have started to take shape against big-league hitters, it’s the third offering — the changeup — that will make Sheffield an effective starter in the coming years, Servais says.

“When you’re still developing guys at this level, you’ve got to throw all of your pitches,” Servais said. “Certainly his go-to pitches will be his fastball and his slider, and it’s probably going to be that for the majority of his career. But, to get through that lineup a third time, you’ve got to have that third pitch.

“When you talk about does he throw 12, 15, 18 of those changeups a game? I think he should. He’s going to be out there 90-100 pitches, he should throw 15-20 of them in a game, picking the right spots.”

Sheffield threw a season-high 14 changeups against the Reds — he threw five, 10 and eight in the three starts prior, respectively — and said having that third option was valuable in spots where he didn’t feel he had his best stuff, but needed to find a way to continue to attack.

“My changeup worked into play throughout the game,” he said after the Cincinnati start. “It’s always nice to have that third pitch. To have it come out tonight, and see it work a little bit tonight, was good.”

It still needs tinkering of course. Sheffield’s changeup has averaged between 86-88 mph — not quite as slow as the Mariners would like to see compared to a fastball that sits at 93.

“In a perfect world, you’d like 8-10 mph slower,” Servais said. “The one thing about his changeup is he does have bottom to the changeup. It’s got some fade, and it’s got some depth to the pitch, so it’s on a different plane when it’s reaching home plate, which is really important.”

That finish can cause batters to swing and miss, or induce ground balls, which is a step in the right direction.

“You would like to see it a little bit slower over time,” Servais said. “The more he throws it, the more feel he gets with it, I think the velocity will back off a little bit and there will be more separation.”

Simply continuing to work his changeup into outings will be key for Sheffield in his final few starts of the season, Servais says. He’s scheduled to pitch again in Sunday’s homestand finale against the White Sox.

“Some days it’s going to be really good, some days it’s not going to be as good, but you’ve still got to throw them,” Servais said. “That’s what we’ll continue to do with him moving forward.”

Lauren Smith covers the Seattle Mariners for The News Tribune. She previously covered high school sports at TNT and The Olympian, beginning in 2015. She is a graduate of the University of Washington and Emerald Ridge High School.