Earlier this season, I wrote about how the Tigers starters were utilizing the changeup more often this season and that it was working to their advantage. Yesterday, I took on Rick Porcello’s rising star and how his use of offspeed pitches were helping him become a bona fide star. Well it’s working for another one of the Tigers pitchers, too.

Anibal Sanchez has been a solid MLB starter for several seasons, so his breakout might be a little less surprising to you, but it’s not less impressive than what Porcello is doing. Here are Sanchez’s strikeouts and walks per 9 since 2009:

He was always a 7-9 K/9 pitcher and his control has been improving each year. But something happened this year. His strikeouts shot way up and that is directly responsible for his career best ERA, FIP, and xFIP and his on pace to be best career WAR. Here are those rates since 2009:

Any quick look at Sanchez’s numbers will tell you he’s striking out more batters and walking fewer, but the walk rate decline has been happening for years. But the strikeout spike is new and it’s correlated with the huge improvement in run prevention. That alone isn’t enough to tell you anything, but consider this. Sanchez is actually getting hit harder when he gets hit. He’s giving up more hits on balls in play (probably because of his defense, but that counts toward his ERA)

And the batted ball data actually makes him look worse as he is giving up more line drives at the expense of groundballs, which we would usually consider to be harder hit and more likely to result in baserunners:

So let’s review. He’s preventing runs better than ever before with more strikeouts and fewer walks. He’s giving up more hits on balls in play and they are likely coming on harder hit balls because he’s giving up line drives. If anything, he’s been unlucky on balls in play. His HR/FB rate will regress up, but that is accounted for in xFIP so we’ve essentially controlled for that explanation. The only explanation that makes sense for why he’s gotten so much better this season is the strikeouts.

But about those strikeouts. He’s not getting hitters to swing more than they used to. And he’s not getting them to swing at worse pitches. Batters are essentially swinging the same amount as they have the last two seasons against him both in and out of the zone:

So they’re swinging the same, but they are making much less contact:

Let’s revisit how he’s adjusted his pitch selection now to get a sense for what might be causing this:

Basically, the key change in Sanchez’s approach is his increased use of the changeup. If we sum this up, we get this story. Sanchez is preventing runs better this year because he’s getting more strikeouts. He’s getting more strikeouts because he’s getting hitters to swing and miss more often, but not based on the location of the pitch. So it has to be about the pitches themselves. And he’s using the change up more. So it’s probably the changeup, or at least the threat of a better changeup.

In fact, if we track his swing and miss percentage on each pitch over the last five seasons, you can see that while he’s doing well with the fastball and slider this year, it’s the changeup that is really driving this breakout over time. He’s gotten swings and misses on his fastball and slider at this rate before, but the changeup swing and miss rate is at an all time high.

In my other life, I’m a social scientist, so I’m not going to sit here and tell you a better and more effective changeup is the only reason Sanchez is better this year, but the evidence certainly points in that direction. He’s getting better results based on an increase in strikeouts. Those strikeouts are the product of more swings and misses, but batters are swinging at the same rate and they are swinging in the same locations. At this point, it looks like the changeup is drawing the most whiffs, and therefore, more of the credit for the uptick in strikeouts.

Sanchez was great down the stretch for the Tigers in 2012, but some people worried about giving a good but not great starter such a big contract. It doesn’t appear as if those concerns were warranted as Sanchez has turned himself in the AL’s best pitcher by FIP, xFIP, and WAR so far this season thanks to better use of his changeup. This is something all of the Tigers starters seem to be doing, but Sanchez is doing it exceptionally well. I’m not sure if it’s Jeff Jones, Alex Avila, or the starters themselves, but the Tigers are striking batters out at a crazy rate and it’s likely thanks to the changeup.

Anibal Sanchez has the changeup to thank for what could be a Cy Young season.