The White Sox bullpen has had familiar faces in the bullpen with Nate Jones and David Robertson the past few years but, like any other major league club, there are a few names that move between the minors and majors, filling in spots, hoping to throw a few strikes and perhaps even reinvent themselves.

Over the course of 2016, Tommy Kahnle was almost never talked about amongst most fans. That’s fine; not everyone can be a superstar. But in 2017, Tommy Kahnle is now the guy everyone is talking about. And I don’t just mean in Chicago either. Yes, that’s how drastic of a step forward Kahnle has taken in just a few short weeks of baseball. Baseball that he wasn’t even aware he would be playing. Kahnle started the season in Triple-A Charlotte; he didn’t even break camp with the major league roster. In fact, the 27-year-old, formerly a part of both the Yankees and Rockies organizations, was only brought up to fill the shoes of the injured Jake Petricka.

What a case of serendipity this has been for the White Sox, who were surely just expecting to see the same Kahnle they’d seen before with spotty command and a few bad outings in Arizona. Wrong.

The White Sox bullpen has been strong so far in 2017 and Kahnle has been a big part of it despite only throwing nine innings. Take a look at these numbers to see just how good the White Sox relievers have been so far:

The White Sox currently lead baseball in ERA and, for more context, they’re leading the league in DRA as well. That indicates the production coming out of the bullpen is not simply flukey baseball stuff or good defense coming to the rescue. The biggest concern is the walk rate—good for just middle of the pack. Without Kahnle, who has only walked one batter on the season so far, the Sox would likely rank even lower.

The reason is because Kahnle used to walk guys. He walked a lot of guys. His walk rate was 18.1 percent when he was with the Rockies. The incredible 3 percent walk rate Kahnle is posting so far in 2017 is of course not quite sustainable long term but, when you watch Kahnle, you can see his stuff looks like it’s here to stay. He’s found his command of the strike zone.

Kahnle is aware that the difference has been huge, yet the changes he’s made have been relatively small. “Everybody knows my fastball command is a little spotty sometimes. I made a few adjustments with my legs, I should say kinda my delivery, it seemed to work,” Kahnle told White Sox Weekly on WLS. “It was more of a shortened leg kick, I guess.”

Kahnle also attributed his recent success to keeping his head turned more toward home plate as he throws. “I usually have tendency to fall off. I worked towards those two things and it’s starting to work.” Kahnle said.

Not only has the ability to repeat his delivery with pinpoint command lead him to a 1.00 ERA and a -0.89 FIP (yes, negative FIP is possible), but he’s actually added velocity to his pitches across the board. Kahnle has seen his average fastball velocity tick up by 2 mph. His changeup and slider have gone up by nearly 5 mph each (sitting at 91 mph and 93 mph, respectively.)

According to PITCHf/x, Kahnle currently had the fifth-highest velocity among relievers this year. That has him ranked alongside pitchers like Aroldis Chapman, Trevor Rosenthal and even ranked above Boston closer Craig Kimbrel. Of those top five in the velocity rankings, Kahnle currently holds the best whiff percentage at 34.8 percent.

It’s well-known throughout baseball that White Sox pitching coach Don Cooper is a mechanical wizard. And though he isn’t much of a numbers guy (In a conversation we had once, Cooper referred to sabermetrics as “the sabermetrics”), Cooper does proves that numbers aren’t everything. Mechanical adjustments can take a pitcher from ranking as a poor strike thrower one year to what Tommy Kahnle is now with just a couple of tweaks. Because the success Kahnle is seeing right now is mechanically based and not simply a ton of luck breaking his way or a poor quality of opponents, folks can rest assured that this Kahnle 2.0 we are seeing may be here to stay. If he is, the White Sox stumbled on quite a beneficial dose of happenstance.