It's one of the worst kept secrets in baseball that Jason Hammel probably won't be pitching in North Side of Chicago for much longer. The 31-year-old signed a one-year, $6-million deal with the Cubs this offseason, hoping to make him this year's Scott Feldman, whom they turned into Jake Arrieta and Pedro Strop at last year's trade deadline. If Hammel keeps pitching as well as he has thus far, the Cubs could get more than what Feldman brought them a year ago.
Though Hammel got roughed up by the Pirates on Wednesday, he's still enjoying the best season of his career. In 83 1/3 innings covering 13 starts, he has a 2.81 ERA, 3.02 FIP, 0.98 WHIP and 76 strikeouts against 18 unintentional walks. The 17.7-percentage-point difference between his 23.2-percent strikeout rate and 5.5-percent walk rate ranks 16th in the majors. He also has limited the damage by surrendering just six home runs.
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Before handicapping if Hammel can keep up his success over the course of the entire season, it would help to explore just what he's doing that is driving his 2014 breakout. His recent start against the Marlins is a great place to start.
Hammel struck out eight in seven scoreless innings, allowing six hits and one walk. Five of those eight strikeouts came on the slider, which has been a dominant pitch for Hammel this year. He has thrown it 30.9 percent of the time and, according to Fangraphs, it rates as the sixth-best slider in the majors this year having saved Hammel 1.94 runs per 100 times thrown. The mighty Giancarlo Stanton appears in the above video twice. The first time he flails helplessly at the slider for strike three, and the second time he taps it back to the mound, where Hammel fielded it and began a 1-4-3 double play.
Digging deeper into Hammel's slider, we can see why it has been especially effective this season. According to movement data from Brooks Baseball, Hammel's slider has had its most downward vertical movement this season. Given that his slider, as evidenced in his outing against the Marlins, is more dependent on vertical break than horizontal break, this is a very good development.
Overall, Hammel's slider has an 18.8-percent swinging-strike rate. Isolating for only sliders that opposing hitters have offered at, his whiff rate jumps to 41.7 percent, which is the ninth highest in the majors according to Baseball Prospectus. Below is a table with results and averages hitters have amassed against each of Hammel's pitches this year. Again, we see the effectiveness of the slider, here, as hitters have managed just a .152 batting average and a .217 slugging percentage.
The next table shows what sort of batted-ball outcome occurs when a hitter swings at Hammel's slider. In addition to whiffing 41.7 percent of the time, they foul it off 24.4 percent of the time. That means they put it in play only about one-third of the time that they swing at it. As the table shows, rarely do they do so with any sort of authority.
Hammel's ground-ball rate on his slider is just shy of 50 percent, and his popup rate is nearly nine percent. Hitters have managed a 19.3-percent line-drive rate against the slider, but that translates to about 12 percent of swings. Any pitcher can live with that total. But even with all the data above, perhaps the best illustration of how good Hammel's slider has been is the final chart below, which is a heat map of the where in or out of the zone he has thrown the pitch this year.
See that box in the bottom right corner, which is down and away to righties and down and in to lefties. Nearly 30 percent of Hammel's sliders have gone to that box, which is exactly where a pitcher wants it when it's a put-away pitch. Not only has the pitch been filthy, Hammel's command of it has been superb.
So it's clear that Hammel's slider is driving his big year. The question before fantasy owners is whether or not Hammel can keep this up. In 2012 while still with the Orioles, Hammel posted a 3.43 ERA, 3.29 FIP, 1.24 WHIP and 113 strikeouts in 118 innings. That season, he saved 1.34 runs per 100 sliders thrown, which was his career high before this season. It's not unprecedented for him to have a high level of success thanks to an effective slider.
At the same time, Hammel's .234 BABIP suggests he has been a bit fortunate this season. His overall line-drive rate is 20.2 percent, while his ground-ball rate is down at 39.9 percent. The slider has been quite effective, but his other offerings have left a bit to be desired. Should the Cubs deal Hammel to an American League team, his stock would certainly take a hit by virtue of losing a handful of pitcher plate appearances each game. Even if he remains in the NL, it's hard to imagine him keeping up this level of production. A 31-year-old pitcher rarely changes his stripes.