Tanner Roark’s dominance via two-seam fastball

Earlier this year, my girlfriend took me to a Nationals game. It was a Saturday afternoon in late April and we had club-level seats, the makings of a perfect day at the ballpark. However, my excitement was slightly dampened when I learned that the Nationals’ starter would not be Max Scherzer or Stephen Strasburg; it was Tanner Roark. Seven innings later, however, Roark had tallied 15 strikeouts in a two-hit masterpiece against the Minnesota Twins.

This has not been the norm in 2016. Roark hasn’t struck out more than seven batters in any other start this season. He has a 19.7 percent strikeout rate, below average for a National League starter. Despite this, Roark has the 10th-lowest ERA in the NL among qualified starters. He ranks fourth among NL starters in rWAR, 14th in fWAR, and seventh in RE24. While this is partially because he is fourth in the league in innings pitched — these are counting stats, after all — these results are still largely unexpected for a pitcher who couldn’t crack the Nats’ rotation a year ago.

Roark isn’t the only low-strikeout pitcher in the mix, though. Jason Hammel and Johnny Cueto have lower ERAs than Roark with strikeout rates just above league average, at 21.1 and 21.8 percent, respectively. Kyle Hendricks has the lowest ERA in the National League and a 22.1 percent strikeout rate. There is more to dominant run prevention than a high strikeout rate. Roark’s success is a bit more puzzling than the rest, though. He owns a K-BB% of 11.8 percent as a starter, the smallest of any NL starter with an ERA under 3.00 (minimum 60 innings pitched).

The simple explanation is this: Roark manages contact as well as any pitcher in baseball. He has the lowest hard hit percentage of any qualified MLB starter, at 23.8 percent. His 25.1 percent soft contact rate is second-best, behind only Hendricks. These two are in a league of their own when it comes to generating soft contact — Steven Wright is next on the list, and he’s nearly two percent below Hendricks — which was recognized by FanGraphs’ Alex Chamberlain back in July.

In that article, Chamberlain points out that Roark has increased his curveball usage, implying that this is the reason why his ground ball rate has gone from 41.4 percent in 2014 — a season in which he posted 3.1 fWAR in 198 ²⁄₃ innings -- to 49.8 percent in 2016. However, this doesn’t doesn’t tell the whole story; in fact, Roark’s curveball has induced a lower ground ball rate in 2016 than it did last season (though a 50 percent ground ball rate is still pretty good).

No, the answer here seemingly lies with Roark’s two-seam fastball. He has cut back on his two-seamer usage slightly this season, but with a 46.3 percent usage rate he still throws it more than twice as often as any other pitch in his arsenal. The average velocity on his two-seamer (and four-seam fastball, for that matter) has declined slightly since last year, but this is to be expected after he spent a large part of 2015 in the bullpen.

Look at where that velocity is compared to 2014, though. Roark is on pace this season to best his inning total from 2014, but is throwing his fastball nearly a full mile per hour harder despite being slightly “past his prime” (fastball velocity starts to decline at age 29, and Roark is nearly 30). His peak velocity is higher too.

Oh, and there’s also more movement on the two-seamer than ever before.

In particular, Roark is getting more vertical drop on his two-seamer than in years past despite throwing it harder. This has resulted in a 55.2 percent ground ball rate when his two-seamer is put into play, up from just 42.0 percent in 2014 and 51.0 percent last season.

Of course, a high ground ball rate isn’t everything. Opponents are batting .277 off Roark’s two-seamer, the highest average against any of his pitches. Six of the 13 home runs he has allowed have come off the two-seamer as well, though he has limited opposing hitters to a modest .099 ISO.

The high ground ball rate does help him paper over some mistakes, though. Roark has induced 22 double play balls this season, the fourth-highest total among MLB pitchers. While this stat is usually dominated by bad pitchers who allow a lot of baserunners — Mike Pelfrey ranks just above Roark on the list with 24 twin-killings — Roark’s excellent ground ball rate on his two-seamer has helped him and his defense keep the basepaths clear.

It will be interesting to see if Roark can continue this level of production going forward. As Chamberlain pointed out, contact managers like Sonny Gray and Marcus Stroman have faltered in 2016, which highlights how inconsistent pitchers with lower strikeout rates can be. Additionally, Roark will be entering his age-30 season in 2017, and could start to lose some of the zip on his fastball. The Nationals can stomach some regression — they do still have Scherzer and Strasburg around, after all — but even an ERA closer to his mid-3’s FIP would make him a valuable commodity considering his cost-controlled salary.

As for him continuing to rank among the league’s best? I wouldn’t bank on it for too much longer, but enjoy it while it lasts, Nats fans. Especially if you end up at the ballpark on one of the days that he starts.

Rob Rogacki is a contributor at Beyond the Box Score and the Managing Editor of Bless You Boys, SB Nation's Detroit Tigers community. You can follow him on Twitter at @BYBRob.