Mike Bolsinger has been impressing many in 2015 with his surprising breakout for the Dodgers, after a lackluster Diamondbacks debut in 2014. This season, he has stepped into the Los Angeles rotation and delivered a sterling 2.92 FIP (and even better ERA) over 62.0 IP in his first eleven starts.
Acquired by the Dodgers in part because of the deceptiveness and high spin rate of his hard curveball (first discovered by Fangraphs' Eno Sarris), Bolsinger has added a slider to his repertoire, and demonstrated himself to be a reliable major league starter.
As Sarris noted in a recent post, a part of this success is due to the similar velocities and glove-side movement of the three pitches (his fastball is a cutter). This season, not only is the margin of velocity between his pitches fairly similar, but the margin of horizontal break between his cutter and curve have shrunk to 1.3 inches, on average.
In fact, even the margin between his slider and cutter is smaller than his cutter-curve margin from 2014. With similar movement and a 6 mph difference, the curve almost acts like a change-up - that is, until vertical movement is considered. There's a 15-inch difference between the drop on Bolsinger's cutter and his curve (per Brooks Baseball).
That kind of deception is freezing up batters. Per Baseball-Reference, Mike Bolsinger has a whopping 37.2 percent strikes looking rate, which is the highest rate in the majors by a 3.2 percent margin (ahead of the Marlins' David Phelps).
By Fangraphs' metrics, his 55.1 percent zone-swing rate is by far the lowest in baseball (minimum 60 IP). He also features the 12th-lowest outside-swing rate, and the lowest total swing rate (39.1 percent).
Bolsinger is also generating the seventh-most ground balls in the majors (57.3 percent), a great sign moving forward. His curve is a great out-pitch, generating 30.2 percent strikeouts on the season, although his less-frequently used slider generates many more swings-and-misses (26.7 percent versus 11.9 percent, per Fangraphs).
This might be a small problem moving forward, as Bolsinger is quietly receiving a little bit of help from his backstop. Despite his very high strikes-looking percentage, Bolsinger ranks towards the middle of the pack in terms of actual pitches thrown in the zone.
As a pitcher who relies so heavily on breaking balls, this might not be a problem - but he also isn't generating a ton of swings and misses. A factor to consider in this case is that this early in the season (this is still talking about a small sample), nine of his eleven starts have been caught by Yasmani Grandal.
Grandal is a pitcher's best friend in that to this point in the season, he has been the most valuable framing catcher in baseball. It is far easier to keep your peripherals in check when your catcher has been worth 13.1 runs above average in framing in less than half a season.
Mike Bolsinger has had a strong first half in 2015. He has added a new swing-and-miss breaking pitch, solidifying him as a major league starting pitcher. He also generates deception and weak, ground-ball contact between his cutter and hard curve.
In his trade to the Dodgers, Bolsinger may have found the perfect situation to for his success, where his ability to freeze batters is compounded by the wide strike zone afforded by his catcher. When a batter isn't sure whether to swing, they don't get the luxury of as many calls on the corners; they get rung up.
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Spencer Bingol is a contributor at Beyond the Box Score. You can follow him on Twitter at @SpencerBingol.