FORT MYERS, Fla. — Everything is a little bit simpler for pitcher Joe Kelly of the Boston Red Sox this spring.

His delivery is simpler. His repertoire is simpler. His role is simpler.

What isn’t simpler is the challenge Kelly presents to hitters. The overpowering way he pitched out of the bullpen in September and October – a 0.51 ERA in 14 appearances, including 23 strikeouts against three walks – made that clear. His newfound ability to command his fastball allowed him to unleash his potential in a way he never could as a starter.

“The thing that’s abundantly clear is he knows what his strengths are and has been able to repeat those more consistently,” Red Sox Manager John Farrell said.

As part of his transition to the bullpen midway through last season, Kelly simplified and shortened the arm action of his delivery. He previously had thrown pitches as if nothing mattered but the radar-gun reading, bringing his arm back as far as it could go and then launching it forward. He instead began to keep his arm closer to his body, giving him more control over the way it moved through his delivery.

The simplified arm action gave him more consistency to his release point and allowed him to stay on top of pitches in a way that would prevent the extra side-to-side movement that so often undermined him.

When Kelly threw a fastball toward the outside corner in September, it stayed on the outside corner. When Kelly threw a fastball toward the inside corner in September, it stayed on the inside corner. No longer did he see his pitches leak back over the middle where they could be hammered.

What Kelly is seeing now can’t compare to September and October – it’s too early for that yet – but it does compare favorably to what he felt a year ago at this time.

“It feels better than last spring,” he said. “It’s not all the way there yet because you need the repetition, but it feels a lot better than where I was last year.”

And because Kelly is pitching one inning rather than five or six, he can simplify his repertoire in the same way. He all but shelved his change-up by September, and several outings saw him throw just two pitches – either his fastball and curveball, or his fastball and slider.

Kelly threw more curveballs than sliders for much of September, but threw twice as many sliders as curveballs in his three playoff outings against Cleveland.

“I can throw them both for strikes early in the count, and I can make both a little bit sharper to try to get a strikeout,” he said. “They’re both good to lefties. They’re both good to righties. I can pick and choose based on the hitter – like if it’s a power hitter or a guy who doesn’t strike out much. But it’s not like there’s one I use to left-handed batters and one I use to right-handed batters. I use them both.”

“The curveball has not been taken out,” Farrell said. “When you have the ability to spin the baseball like he does, you’re not going to take that pitch away.”

What Kelly has shelved is his change-up, at times in his career his best secondary pitch. He threw more change-ups than curveballs in 2015, a season in which he made 25 starts. He didn’t throw a single change-up in his 17 relief appearances in the second half of the 2016 season. He’s not throwing his change-up now, either, except on occasion while he’s playing catch on flat ground.

The disappearance of the change-up all but drives home the change in role for Kelly. He’s no longer a four-pitch starter, trying to command his fastball for 90-plus pitches. He’s a two- or three-pitch reliever, something of a secret threat in front of Craig Kimbrel in the Red Sox bullpen.