A 36-year-old who threw 14 innings in the majors last season had the most interesting offseason in baseball.

Craig Breslow, the former Red Sox left-handed reliever and a free agent, still has a lot of work to do. But he’s about two-thirds of the way through a project meant to rehabilitate not his arm, but his entire arsenal — and by extension, his career.

On Monday, Breslow unveiled a new arm slot to scouts from about a dozen teams at an indoor facility in Waltham. The Red Sox were there, as were the Mets, Cubs, Blue Jays, Twins and Reds, among others.

He’s not a sidearmer, but Breslow has dropped down, adding a two-seamer with heavy tail.

“That’s going to be the most striking difference from what people are used to seeing,” Breslow said. “I’ve been a predominantly four-seam guy, and now a two-seamer that’s got true two-seam action. It’s just such a different pitch than what people had ever seen me throw.”

Breslow doesn’t want teams to believe him based on what he says, or how he looks in bullpens, however. He’s got numbers, and that’s the point.

Breslow, long known in baseball circles for his smarts, has gone a step further in baseball’s Big Data era. He set out to learn about some of the best pitchers — and their best pitches — to see if he could mimic some attributes, such as horizontal and vertical movement.

He’s not trying to mimic just one pitcher’s pitch exactly, but he’s reviewed many.

“To say, ‘I’m going to try to make Andrew Miller’s breaking ball,’ would probably have been a fool’s errand, given that he’s 6-foot-8 with longer levers, longer fingers, etc.,” the shorter Breslow said. “But to say, ‘This type of breaking ball, from this slot with this action, is an effective one, let’s see how close we can get to that,’ is a much more plausible undertaking.”

In October, Breslow had 9.45 inches of horizontal break on the two-seamer, based on numbers he provided to the Herald and obtained through a pitch-tracking system called Rapsodo.

In a January sampling of pitches determined to be accurate, he had 1 foot, 6.35 inches of movement — nearly 9 inches more. His vertical movement, meanwhile, had increased about 6 inches.

“In the beginning, I remember taking rides with my wife (Kelly) to go visit family and me driving her, being on a laptop and literally kind of being like … ‘OK, who’s got the best sinker?’ ” Breslow said. “Let’s look at Zach Britton: (he’s) left-handed, dominant sinker, induced a ton of groundballs. Let’s take a look at what kind of action he gets. How did his PITCHf/x numbers compare to mine?

“OK they’re obviously a lot better for a lot of reasons. Let’s kind of decide if we can get X percentage closer to that, then we’ll call that a success. … We need some way at the end of all this (to say) did we achieve the goal or not?”

One goal is to be with a team when major league camps open next month, and he hopes interested teams will project what he’ll look like in April, in June.

It’s still just January, and peaking in January would be a mistake. He wasn’t sitting in the 90-mph range yet Monday, for example.

A Connecticut native, Breslow has the help of another New England product and ex-Sox lefty, Rich Hill of Milton. They’re throwing buddies, working out in different areas: Waltham, Canton, Boston College among them.

A wonderful success story in his own right, Hill signed a $48 million deal with the Los Angeles Dodgers this winter after harnessing his curveball (and its many variants) the last couple years, including a brief stint with the Sox in 2015.

“I’ve caught a lot of guys,” Hill said. “But even when you’re playing catch, it’s uncomfortable to catch (Breslow’s two-seamer) because it has such late movement and depth to it. It’s something that I think is just going to improve as he gets more and more comfortable with this new arm angle.”

Muscle memory and repetition is the trick now.

The sea of data Breslow has sifted through can be murky. On track to become a doctor when he was younger, Breslow took physics classes but came to appreciate them more after the fact. How Rapsodo captures information is different than how PITCHf/x does, and the numbers listed at BrooksBaseball.net, for example, are not raw PITCHf/x data.

"It wasn’t always a very clear apples-to-apples comparison," Breslow said.

Breslow’s not just tracking his pitches, but his exercises and strength gains.

About four times a week, Breslow visits Mike Boyle, the former Sox strength and conditioning coach. He goes for two and a half hours, grabs a bite, then visits Mike Reinold — another familiar name, because he was once the Red Sox’ top athletic trainer.

“We put some force monitors onto his body and analyzed them while he threw, and his force (exerted) actually went down with his new mechanics,” Reinold said. “All of a sudden he’s got huge horizontal movement, got a brand new two-seam that he never really had before and the stress on his arm went down. We were taken aback.”

Now, Breslow may have his career back.

Follow Boston Herald Red Sox beat writer @EvanDrellich on Twitter and on Facebook. He can be reached by email at evan.drellich@bostonherald.com.