FORT MYERS, Fla. -- Newly acquired Twins reliever Steven Okert has worked out alongside teammate Griffin Jax for the past three offseasons in the Phoenix area -- and Okert calls Jax an “animal.”

When Okert gets there around 9:30 a.m., Jax is already mid-workout. When Okert leaves after noon, Jax is still hard at work.

“I feel like he's done with his workout, and then I look over, and he's doing more,” Okert said. “I'm like, ‘Griff, I thought you were done an hour ago. You're back in here doing more stuff?’”

That’s the kind of offseason that leads to Jax showing up to camp having added -- or rather, revisited -- another new pitch that has been turning heads this spring: a curveball that averages an eye-popping 86 mph, with nearly 14 inches of induced break that he hopes can be the next step in the continued evolution of his arsenal as part of the back end of the Minnesota bullpen.

“With my position in the bullpen, it's so hard to have a plan for six pitches,” Jax said. “So we generally try to simplify it a little bit. At the same time … I think it'll get a lefty and a righty out no matter what.”

Jax and Brock Stewart are the most likely candidates for save opportunities with Jhoan Duran out to start the season due to a right oblique strain, though Jax says the Twins haven’t necessarily approached him outright, instead maintaining their typical message: Just be ready to pitch.

“I don’t think that’s helpful trying to give people titles and things like that, so we’re not going to do that, but he’s a really good late-inning Major League reliever who I will pitch against anybody,” manager Rocco Baldelli said.

When Jax does pitch, he gets those sorts of high-leverage opportunities because of unique pitch metrics like this. Everyone in the league knows that Jax is going to attack most dominantly with his sweeper, which he knows is a “unicorn” pitch of sorts due to its combination of velocity and movement.

Jax’s sweeper -- which he threw 52.8 percent of the time last season -- averaged 86.7 mph with 13.5 inches of movement to his glove side (away from right-handed batters). That’s 5 mph harder than the league’s average sweeper at 81.8 mph, and no pitcher threw a harder slider of any kind with more lateral movement.

It’s a truly great pitch -- but the league knows that’s how Jax is going to attack. Jax remembers that stretch last season when he struggled due to weakly hit singles, miscues and other weird plays that ballooned his numbers despite not being hit so hard -- and he’s trying to evolve the arsenal to keep hitters more off-balance and stop them from sitting on the slider.

“They're big league hitters, too; they're going to be able to make adjustments like anybody else,” Jax said.

It’s nice for him when he can pull a curveball like this out of his back pocket.

Jax loves to tinker, and he knows that shorter stints, added strength (he’s up 15-20 pounds since his starting days) and his arm’s natural ability to supinate give him the opportunity for some elite breaking pitches.

So, Jax toyed around with the curveball that he’d previously abandoned, and found that it had jumped more than 6 mph in velocity since his starting days. He refined it and took it to the Twins -- and they liked it, too, he said.

The raw numbers on that curve are also eye-popping -- as have been the bad swings that it has induced from good hitters this spring. The 86 mph average would have been the 11th-hardest curveball in baseball last season, and remember how it breaks nearly 14 inches (not counting gravity)? None of those harder curveballs had more than 9 inches of such break.

Couple that with a sinker he introduced last season to go into righties and keep them from sitting on the sweeper and fastball over the outer half -- and Jax’s work has him continuing to improve when his team needs it most.

“I'm one of the smallest pitchers on the team, or person on the team in general,” Jax said. “I have to do most things right in order to be able to throw as hard as I do. So I can dive into that deep and just really understand what I need to do in terms of body prep, recovery, all the little things that go into it. I kind of pride myself in that.”