Before the calendar turned from August to September, Chris Sale looked like the front runner for the AL Cy Young award. Overall, he's still had a fantastic 2015 campaign, but his four starts this month have hurt his chances at taking home that honor. In September, Sale's 5.40 ERA / 4.69 FIP / 2.80 xFIP is in stark contrast to his 3.20 ERA / 2.40 FIP / 2.55 xFIP line from April-August.
By FIP, Sale's September this year is the worst month of his career. By HR/FB, it's the worst month of his career. By ERA, it's the second-worst month of his career. The worst month, Mar/April of 2011, saw a 5.91 ERA in only 10.2 innings. Sale has thrown more innings this month than that month, and given the FIP it would seem this month is the worst overall of his career (so far). Unfortunately for him, Sale's struggles don't seem to be tied to one factor, but rather a variety of reasons.
One of the notable changes has been in Sale's pitch selection. While there aren't dramatic changes across the board, his fastball and slider usage have shifted.
Though Sale didn't use his four-seam fastball very often from April through August, it was at least an option; however in the month of September, he hasn't used it once. The biggest difference is in slider usage, which has increased by about five percentage points, or about a quarter more. If batters were suddenly having more trouble hitting that pitch, this strategy would undoubtedly make sense, but that hasn't been the case.
As his slider usage has increased, it's unfortunately lost nearly all of its value, but the slider is not Sale's biggest issue. Seemingly at the flip of a switch, his two-seam fastball has gone from one of the most valuable pitches in all of baseball to one of the worst. In the month of September, Sale's wFT ranks last in MLB, which could be related to the loss of vertical movement in the pitch. From April through August, Sale averaged 5.9 inches of vertical break on his two-seam, but this month it's 4.8.
It's difficult to pinpoint why he's lost some vertical movement, but it's possible that it has something to do with the change in his release point.
At the beginning of the season, not only were all of his pitches coming out of relatively the same horizontal arm slot, but also they were all closer to the center of the pitching rubber. As the season has progressed, he's released the ball farther away, and the difference between each pitch has become more noticeable. Sale was fairly consistent from May through August, but in September there has been a notable increase in his horizontal release point along with some convergence between his sinker and changeup and his four seam and slider.
Another factor in Sale's recent decline can be attributed to hitters not chasing or missing as many of his pitches as they did early in the season.
Unfortunately for Sale, he's experienced a drop in O-swing, swinging strike, and first-strike percentages. The most worrying of these three statistics is undoubtedly the lack of swinging strikes, but it's interesting that it hasn't negatively impacted his strikeout rates all that much. Over his last four starts, Sale has a K/9 of 11.57 compared to 12.03 for the first five months.
The biggest reason for Sale's subpar month is likely the type of contact he's allowing. His hard-hit rate has skyrocketed, and so too has his HR/FB ratio.
Sale's hard-hit percentage has nearly doubled, while his HR/FB ratio has gone up by 161 percent. According to Baseball Heat Maps, his average batted ball distance on home runs, fly balls, and line drives has increased from 258.3 feet to 286.3 feet, an increase of 28 feet.
He's had a fantastic overall season, as nearly every pitcher in baseball would gladly accept an ERA of 3.47, an FIP of 2.67, 259 strikeouts, and a 5.9 fWAR. It could be small sample size; it is kind of funny that the worst month of his career is coming during the best season of his career (by fWAR and fWAR/200 IP). Despite the small sample size, there is a confluence of factors showing that Sale just isn't the same pitcher as he was for most of 2015.
. . .
Matt Goldman is a Featured Writer with Beyond the Box Score and a Contributing Editor at MLB Daily Dish. You can follow him on Twitter at @TheOriginalBull.