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Kenley Jansen is undefined

Kenley Jansen has a record-breaking start to the season, thanks to his many strikeouts and nonexistent walks. Literally nonexistent!

MLB: Los Angeles Dodgers at St. Louis Cardinals Jeff Curry-USA TODAY Sports

The story of the 2016-17 MLB offseason was the quantity of elite bullpen arms available in a free agency cycle that was otherwise barren. Arguments raged on about who was the best of the three big names: Aroldis Chapman, Kenley Jansen, and Mark Melancon. Regardless of which was the better player to sign, there’s no argument about who has been the best so far this season. Injuries to two of the three are a part of that, but even if all three were healthy, the tremendous display of talent Kenley Jansen has put on for the Dodgers would be hard to match.

In fact, Jansen is in the midst of a record-breaking start to the season. In Milwaukee on Friday, he set a record for strikeouts without a walk to start the season at 36. Since that record-breaking night he has improved his mark to 40 strikeouts without registering a single walk. That is, in a word, good.

He has done so with essentially just a single pitch. He throws a cutter 86 percent of the time that has averaged a velocity of 93.8 mph, along with a very occasional slider (7.3 percent) and sinker (6.7 percent). Closers can thrive using just a single pitch because they’re facing hitters for typically just a single inning, and almost never more than once. They can also thrive when that pitch is in the mid-90s with nasty movement. Rather than muck through data on average inches of movement in each direction, just take a look at back to back cutters Jansen threw the other night in Milwaukee. It’s disgusting.

GIF via MLB.com

Aside from pure nastiness, Jansen is known for his ability to locate his cutter, and change the speed from pitch to pitch. The cutter is at its best in terms of generating whiffs when it’s high in the zone, but he’ll work it anywhere. Perhaps the best demonstration of the pitch’s dominance is where he puts it with two strikes. He tends to throw it up in the zone, where gets all those whiffs, but he is willing and able to put it anywhere. That keeps hitters guessing about where this 93mph pitch with movement is going to end up, and that’s a good thing.

Zone profiles from Brooks Baseball can best demonstrate these tendencies. On the left is his whiff rate in all counts, and on the right is his usage in 2 strike counts.

He pounds the zone and generates whiffs. That has led to a ton of strikeouts despite the Dodgers keeping him from getting a lot of work. He’s pitched in just 23 innings, but he’s struck out 47.1% of the batters he has faced. That’s pretty good.

Eventually he will walk someone. It’s hard to predict when that will happen, especially because he simply looks so dominant right now. According to Baseball Reference’s Play Index, the highest number of strikeouts without a walk at any point in the season is Dennis Eckersley at 46. The way Jansen is going right now, he might just catch that. While he hasn’t received a lot of playing time so far this season, the Dodgers will be extremely glad to have the best version of Kenley Jansen in the back end when playoff time comes.