Last Friday night, Mike Foltynewicz threw a complete game for the Braves during which he struck out 11 Nationals — including Bryce Harper twice — and walked just one, while allowing two hits and zero runs. That’s the kind of performance that tends to make people like me, who don’t otherwise spend all that much time paying attention to what Mike Foltynewicz does with his days, sit up and take notice. But for Braves fans, Foltynewicz’s dominance probably didn’t come as quite that much of a surprise. Foltynewicz has been getting better for some time now:

It took his ERA a little while to catch up to his FIP thanks to some poor results at the end of the 2017 season, but he’s all caught up now and then some. Right now, Foltynewicz owns the eighth-best park-adjusted FIP in the National League and an even better ERA. After generating just 1.8 WAR across 28 starts last season, he’s up to 1.6 fWAR through just 12 starts this year. What’s changed?

One can’t say for sure, of course. If forced to guess, however, I’d say it has something to do with the difference between two numbers. The first is 54.9. That’s the percentage of the time Foltynewicz threw either his fastball or his slider in 2017. The second is 68.9, which is the equivalent figure for 2018. A year ago, Foltynewicz was a fastball-sinker-slider pitcher, in that order, with a changeup and a cut fastball that he threw only occasionally. These days, it’s probably fairer to say that Foltynewicz is a fastball-slider-sinker pitcher, in that order, with the same two backups for emergency use.

Foltynewicz has been able to make that change because, well, his fastball and his slider are simply much better pitches this year than they were just a year ago. He’s added about a mile an hour to his fastball — putting back to about where it was when he debuted with the Braves back in 2015, albeit with better command — and he’s subtracted about the same amount from his slider, bringing it down to around 85 mph, as opposed to the 86 or 87 it was sitting at for the past two years. The net effect has been around 2 mph of increased separation this year, without much change in either horizontal or vertical release points. The results have been, well, striking:

And lest you think I’m trying to wow you with fancy GIFs of Bryce Harper looking foolish (which, I trust, are almost always welcome, as a reminder that baseball is a game in which even the greatest among us fail far more often than they succeed, as do we all), here’s some data for you: last year, Foltynewicz’s fastball and slider were worth a combined 1.6 runs, according to Pitch Info. This year, that figure is 14.4. By focusing on separating his bread and butter (the fastball) from his best pitch (the slider), Foltynewicz has been able to elevate both.

One more piece of data for you, in the service of the same story. Here’s a plot of each and every pitch Foltynewicz threw in 2017, with vertical movement plotted on the x-axis and its horizontal movement plotted on the y-axis:

And here’s the same plot, but for all of Foltynewicz’s 2018 pitches:

What the latter graph appears to reveal is a lot more crispness and consistency in the execution of Foltynewicz’s pitches this year and — here, again, is the important part — a great deal more distinction between his four-seam fastball and his slider. That distinction, along with the velocity separation I’ve already mentioned, has likely allowed Foltynewicz to feel somewhat more comfortable going to those two pitches in quick succession, without feeling the need to throw his other pitches into the mix quite as often has he had been used to in previous years. In previous years, hitters might not have had to worry quite as much about which was which. This year, they do.

There are, I suppose, two ways of thinking about how best to dedicate one’s limited time to self-improvement. One approach is to attempt to shore up weaknesses and make them, at the very least, less bad than they were before. This approach, the theory goes, will creates a more well-rounded and presumably better product. But baseball isn’t really a game that rewards being well rounded, absent a stand-out skill (except, of course, in the varied forms of Bartolo Colón and Mike Trout), and so this was not really a path that was open to Mike Foltynewicz.

Instead, Foltynewicz appears to have identified his strengths and made them stronger. The result has been a marked improvement in what was already his best pitch (a slider) and a change in the way in which he throws his most common pitch (the fastball) to complement it. Foltynewicz has always walked a few more hitters than you’d like him to, and that hasn’t stopped this year — his 10.6% walk rate is as high as its ever been — but Mike Foltynewicz has also never struck out nearly 30% of the hitters he’s faced, either, and that’s what he’s doing this year. He’s running towards his strengths, and it’s working.