Inside Michael Tonkin's climb to the top of the Yankees' bullpen trust tree

The Yankees were in the 10th inning of a back-and-forth affair in Milwaukee, and Michael Tonkin was in a bind. His offense regained the lead in the top of the inning, and manager Aaron Boone called on him, the newest member of the Yankees bullpen, to close things out.

Excuse us? A guy who never pitched for this team — or really in high-leverage situations at all — is getting a save opportunity in his first appearance?

Tonkin had arrived in Milwaukee early that morning after being claimed on waivers by the Yankees the day before, and was now being trusted in the biggest moment of the game. Boone did not want to risk burning out his all-world closer, Clay Holmes, so it would be Tonkin's job to shut the door and prevent a comeback.

Being thrust into this situation after a long night of waiver limbo travel did not bode well for Tonkin. He gave up the tying run in the 10th, then came back out for the 11th and allowed the Brewers to walk it off before recording an out. He seemed destined to be cut as soon as the Yankees needed a fresh arm.

But a funny thing happened after that rough night in Milwaukee. Tonkin started performing better. He rebounded so nicely that, when Nick Burdi was ready to come off the IL two weeks later, it was Ron Marinaccio who was sent down, and Tonkin's roster spot was preserved.

The Yankees' trust in Tonkin has been well deserved. As of June 17, the only earned runs he has allowed in a Yankee uniform came in a mop-up outing on May 22 against Seattle at the Stadium, where he gave up two in a 7-3 win. So how does a guy with a 6.00 ERA, who had already bounced from the Mets to the Twins to the Mets again, almost instantaneously become a stud for a team with World Series aspirations?

There are a few different answers to this question. But the most relevant one might be that the Yankees have helped Tonkin mix his pitches a little better, which has kept hitters off balance.

In 2023, and in his pre-Yankees tenure of 2024, Tonkin was heavily reliant on his mid-90s sinker; a good pitch with decent movement in a vacuum, but relatively easy to get a hold of when batters know it's coming. In April, Tonkin was more often than not using his sinker to get ahead of batters, throwing it around 60% of the time in 1-0 and 1-1 counts, and using it almost exclusively in more extreme hitter's counts. Batters swung at it often, whiffing on occasion, but batting .345 against it with a .483 slugging percentage throughout the month.

Fast forward through May and June, his first two full months with the Yankees, and Tonkin has made it much harder for hitters to know what's coming. He now has a lot more confidence in his slider, throwing it at about the same rate in those 1-0 and 1-1 counts as he does his sinker. Perhaps even more consequentially, he's dropped his sinker usage below 50% in 2-0 and 2-2 counts, leaning on other tools to fool opposing hitters instead of giving them something to hit.

What he's throwing instead on 2-0, and at a higher rate in general, is a sweeper. Tonkin had used a sweeper before as a sort of experimental, second type of slider, but the Yankees seem to have him throwing it with more regularity. It has some great horizontal movement, breaking 2.6 inches more towards a righty than an average sweeper, while dipping just an inch on the vertical plane, causing batters to swing over it more often. He's still only using it just 6.8% of the time, but that rate should increase as Tonkin's trust in the pitch does.

These changes in pitch mix, and Tonkin's growing trust in his secondary stuff, have directly lead to his great results in the Bronx. He's still not going to dominate hitters by a pure "stuff" standpoint, but by using his pitches more effectively he's been able to increase his ground ball rate to 48.3%, by far his best while throwing a full workload of innings.

Part of that increased success with ground balls comes from Tonkin's newfound ability to miss barrels; his barrel rate and hard hit rate have declined steadily since joining the Yankees, with the former now resting at an elite 3.4% mark.

Those peripherals have not only preserved Tonkin's spot on the roster, but have given him results that have graduated him from fringe mop-up guy to trusted back-end reliever. His 0.81 ERA since joining the team on April 26 is the best in the Yankee bullpen during that span, and as of June 17 he has yet to give up a home run as a Yankee.

Preventing those dramatic swings that home runs provide is key in late, close games, and the Yankees' coaching staff has recognized that Tonkin, with his retooled pitch mix and propensity for soft contact, can be their man when they need him.