Steven Matz was effective in all six of his starts in 2015, striking out at least six batters in four of those outings and limiting opposing offenses to three or fewer runs in all six of them. However, Matz didn’t show the world the excellent pitcher he would become until his penultimate start of 2015 on September 8 against the cross-town rival New York Yankees. That was the start when he threw his first major league slider, and it helped him limit the Yankees to one run over six innings and then strike out eight Cincinnati Reds six days later to close out his season.
That new pitch has become an important part of Matz’s repertoire in 2016. Over his first 11 starts this season, Matz threw his slider on 12.7 percent of his pitches, a similar ratio to his other off-speed pitches, a curveball (13.0 percent) and a changeup (11.1 percent). However, four starts ago, Matz cut back heavily on his slider usage, and prior to his pushed-back-a-day June 30 start, we likely learned why. Matz felt tightness in his elbow after his previous start, and an MRI revealed that he had developed bone spurs in his pitching elbow.
I tend to panic whenever I learn about any issue around the elbow for a pitcher, but Matz has pitched twice since the revelation of his bone spurs and has been effective. He struck out a total of 12 batters, walked 4, and allowed just 5 runs over 12.1 innings against the Cubs and Marlins in those starts. More importantly, at least based on my perception of injury indicators, Matz has not experienced any decline in his velocity. Prior to June 18, he averaged 93.4 mph on his fastball, and he has averaged 93.9 mph since. The only stand-out change, then, is the drop in his slider usage from 12.7 percent to 3.1 percent.
|Period||FB%||SL%||CU%||CH%||FA Velo (mph)|
|All of 2015 (6 Starts)||68.4%||1.9%||19.8%||9.9%||94.3|
|Before June 18, 2016||62.8%||12.7%||13.0%||11.1%||93.4|
|Since June 18, 2016||57.7%||3.1%||19.7%||18.4%||93.9|
Matz’s reduced reliance on his slider is probably a result of discomfort, but what’s interesting is how similar it has made him look to his 2015 self before the slider was a part of his repertoire. From then to now, Matz has traded close to 10 percent fastballs for 10 percent more changeups, but otherwise he looks similar in his pitch ratios, fastball velocity, and swinging strike rate (8.5 percent then, 10.0 percent now) to last season. That recent 10.0 percent swinging strike rate from his past four starts is also identical to the rate Matz had prior to June 18 this season, and while not top-end, it puts him in company with exceptional starters like Jake Arrieta (10.8 percent), Chris Sale (10.5 percent), and Julio Teheran (10.0 percent).
To whatever extent you want to put stock in the eight starts Matz has made both prior to the introduction of his slider last season and since decreasing his slider usage on June 18 this season, he has a 3.56 ERA with 8.1 strikeouts and 2.9 walks per nine. For his career, he has positive run values for his fastball, curveball, and changeup using Baseball Info Solutions’ pitch type classifications. Matz may require offseason surgery to remove the bone spurs, but every indication in the short term is that he can pitch with a similar effectiveness with a change in his pitch mix.
Scott Spratt is a fantasy sports writer for FanGraphs and Pro Football Focus. He is a Sloan Sports Conference Research Paper Competition and FSWA award winner. Feel free to ask him questions on Twitter – @Scott_Spratt