CLEVELAND — Tommy Kahnle is persistent.

The visiting clubhouse at Progressive Field features an arcade-style video-game machine that allows the user to choose from a variety of original Nintendo and Sega games. Kahnle, who will turn 28 next month, is old enough to have remembered the 1990s and played the eight-bit game systems. For two days in the clubhouse, he tried his hand at a variety of the games he played as a kid, more interested and focused on beating the games, more willing to hit reset and begin anew after each failed victory, than anyone else in the clubhouse.

And it is perhaps — in part, at least — that sort of persistence which has allowed a once wild arm DFA’d by the Rockies in November of 2015 to emerge as one of the most dominant relievers in the game. Jeff Sullivan recently investigated Kahnle’s curious and dominant April, and Kahnle has only continued to be something of the Craig Kimbrel of the AL Central.

The only pitcher striking out a greater percentage of batters than Kahnle (47.3%) this season is Kimbrel himself (55.6%).

More exhibits of evidence:

The only pitchers featuring superior K-BB% marks are Kimbrel (50.5 points) and Kenley Jansen (44.8).

The other amazing Kahnle Fact: he has the fourth-lowest zone-contact rate among relievers (71%). Batters both chase out of the zone and struggle to hit him in the zone. It’s an attractive combination. He has now sustained this success for better than a third of the season.

Kanhle has always had good stuff. His four-seam fastball ranks seventh in velocity among relief pitchers’ fastballs, and 31st in whiff-per-swing rate, according to the Baseball Prospectus PITCHf/x leaderboards. He said he throws a traditional four-seam fastball but the pitch has some natural cutting action.

He’s second among reliever in whiff per swing (56%) on his primary secondary offering, a darting changeup.

While his fastball velocity is up from 94.6 mph in 2014 to a career-best 97.9 mph this season, while his changeup has better fading action away from Coors Field as one would expect, the secret to Kahnle’s success actually isn’t a secret at all.

“Getting ahead of hitters, really,” Kahnle told FanGraphs. “It’s tough to get guys out when you are falling behind a lot. It’s even tougher to strike guys out when you are not ahead. I would credit it to me getting ahead and these adjustments to mechanics.”

Kahnle has trimmed his walk rate to a career-low 6.6% this season, down from a 16.6% last season. His career average is 13.1%. His first-pitch strike rate has jumped to 60.4% from 52.8% a season ago, and from 52.3% for his career. His zone percent has increased to 50.5% from 47.3%.

For his career, Kahnle has been ahead of hitters in 214 plate appearances. In 239 plate appearances batters have been ahead of Kahnle. But this season, through Sunday, Kahnle has been ahead in the count 36 times compared to the hitter being ahead 23 times.

Consider the old Kahnle, and this infamous walk-off walk from last June:

And the new Kahnle dotting 100 mph:

With a wipeout changeup:

He’s more often getting heading in counts and is more often producing two-strike anxiety in hitters, as his swinging-strike rate has jumped from 10.8% to 17.0%.

Said Chicago White Sox pitching coach Don Cooper to The Athletic back in April: “The only thing between him and staying here forever is just throwing his fastball, his breaking ball, his change over the plate.”

And Kahnle is throwing his pitches more often over the plate.

Consider the fastballs he threw to left-handed hitters last season:

his season ….

And this season:

Kanhle credits some mechanical changes and work with Cooper to turning his career around. He has worked to lower his leg kick since last season. “I used to come up a little too high… It would cause a lot of things to go on,” Kahnle said. He also tried to have his back leg not dip quite as much as it did earlier in his career, causing him to elevate pitches and get inconsistent with his release point. He also developed a glove “tap” last year to get his “arm out quicker.”

But the most important change, he said, was keeping his head focused longer on its target, the catcher’s glove.

“A lot of people had talked about keeping my head on line, but I had never understood what they meant,” Kahnle said. “I kind of figured it out towards the end of the spring this year.”

Sometimes players don’t understand the language of a coach, sometimes there is a communication gap, and Kahnle said he had to develop a feel for what coaches meant by “staying on line.”

One day in Arizona this spring, he decided he was going to focus on the catcher’s glove as long as his he could. He was going to keep his focus there as close to his release point as he could, until his delivery took him somewhat dramatically to the first-base side of the pitching mound.

“I finally started doing it. I guess it worked,” Kahnle said. “All of the sudden, this year, it started clicking.”

And if Kahnle has really found a new level, if he’s really given the rebuilding White Sox a relief ace on the cheap, then it will be one of the better finds of the 2015-16 offseason.

The story of Kahnle is one of persistence and it’s also one of failure. This a pitcher who, like so many others before him, failed to pitch successfully at Coors Field. It was pitching at Coors that perhaps accelerated Kahnle’s realization that he had to make changes, that he had to be open to significant adjustments.

“Especially when I started to fail in Colorado, I knew I needed to change some things,” Kahnle said. “It was last offseason I really started to work on some things.”

Pitchers shed by the Rockies often come with a discount because they come with messy performance lines. But Collin McHugh figured it out at sea level in Houston after leaving Coors Field, as has Juan Nicasio in Los Angeles and Pittsburgh, as has Drew Pomeranz (at times) in San Diego and Boston. If you were willing to take a project, there was upside in Kahnle. A failed Rockies pitcher with stuff, a willing and persistent experimenter. Kahnle is looking more and more like he’s reached a new level, an elite level.