BALTIMORE — Joe Kelly has a better chance of raising the next Zach Britton than being the next Zach Britton himself, for one important reason.

“He’s left-handed,” Kelly said. “That’s why I’m trying to make my son left-handed, so he can be better than me.”

Still, Kelly and the Boston Red Sox have at least a little reason to be intrigued by what Britton has done for the Orioles, and what that might mean for Kelly.

A failed starter with a career ERA of 4.77 in more than 250 big-league innings three years ago, Britton will receive Cy Young Award votes thanks to a season in which he has compiled a 0.59 ERA with 45 saves for Baltimore. Since becoming a reliever full-time, Britton has a 1.42 ERA in almost 200 appearances.

As a starter, Britton emphasized a heavy sinker that sat at 93 mph and included with it a moderate dose of change-ups and sliders. As a reliever, Britton throws almost nothing but that heavy sinker, a pitch that moves out of his left hand the way some sliders move out of some right hands. In short stints he can ride it up to 99 mph.

Kelly might still get another shot as a starting pitcher for the Red Sox next season. The team has yet to have a conversation about that either way. That will wait until after the season ends.

Kelly hopes to get another shot at starting. He believes some mechanical adjustments he made in the bullpen, refining his arm slot and the position of his hand on the baseball as he releases it, would translate back to a starting role.

“It’s not a finished product but what I’ve been working on feels a lot better, for sure,” he said.

The Red Sox acknowledge Kelly has had a chance to prove himself as a starter in five different seasons, twice with the Red Sox, and always seems to wind up in the bullpen instead.

Kelly had a 4.82 ERA in 25 starts for the Red Sox last season and an ugly 8.46 ERA in six starts this season before a succession of injuries. A Boston team that will see Junichi Tazawa, Koji Uehara and Brad Ziegler file for free agency after this season might bring Kelly back as a reliever next season.

As a starter, Kelly offered a four-pitch mix – mid-90s fastball, change-up, curveball and slider. As a reliever, he’s seen his fastball jump from 95-96 on average to 98-99 on average, and the Red Sox appear on the verge of settling on the secondary pitch that works best for him. It might offer the key to it all.

Some relievers can get away with one pitch. Britton throws his sinker almost exclusively as a closer. Los Angeles closer Kenley Jansen throws almost nothing but his cutter. Andrew Miller of Cleveland throws his knee-buckling slider more often than his fastball.

“Having one just completely dominant pitch is the hallmark of those guys,” Red Sox pitching analyst Brian Bannister said. “With Miller, it’s leveraging the slider. With Britton, it’s leveraging the sinker. They’re just such outliers and a hitter only gets one shot at them. … Not every pitcher has that outlier pitch.”

Even more than righties, lefties like Britton, Miller and Sean Doolittle of Oakland can get away with relying on a single dominant pitch because hitters see pitches like those from lefties so much less frequently.

Righties tend not to be able to get away with throwing just one pitch, even in relief. Jansen and Mariano Rivera have done it, as have a handful of others. More common for righties is the profile of Dellin Betances of the Yankees and Craig Kimbrel of Boston, who use a fastball-curveball mix to get their outs.

For Kelly, a mid-80s curveball with an off-the-charts spin rate could unlock his potential as a reliever.

In a September that has seen Kelly strike out 11 and walk three without allowing a run in 72/3 innings, he’s almost entirely ditched his slider and change-up in favor of his curveball.

“Kelly spins the ball as well as anybody in baseball,” Bannister said. “Everybody talks about his fastball but he’s got a power curveball. In relief, he can showcase that much more often.”

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