Jon Gray Is Gray(t) Again. What Has Changed?

Last year, the Colorado Rockies had a very impressive season. After 162 games, the Rockies and Dodgers both held the same record — 91-71 — in which case an all-decisive game 163 was necessary. Colorado ended up losing in Los Angeles, but ultimately went on to defeat the Cubs in the NL Wild Card Game, advancing to the NLDS to face Milwaukee. Their playoff run did not last long, however, as the Rockies proved to be no match for the Brewers, who swept them handily three games to none.

If you were to ask a knowledgable Colorado Rockies fan during the preseason leading up to the 2018 campaign, “Will the Rockies make the playoffs if Jon Gray posts an ERA north of 5.00?” they would have most definitely answered “no.” If you were to ask them, “Will Jon Gray post an ERA north of 5.00 in this upcoming season?” they would also most likely have answered “no.”

Defying the odds, Jon Gray, the Rockies’ 2018 opening day starting pitcher and blossoming front-of-the-rotation arm, had a terrible year in every way possible. His ERA was 5.12 and his WHIP was 1.35. It’s worth mentioning that advanced metrics suggested that he was a much better pitcher than his ERA and WHIP would imply…

  • FIP: 4.08
  • xFIP: 3.47
  • SIERA: 4.18

One could initially try to blame Gray’s struggles on the offense-inflated Coors Field, but he actually posted a higher ERA on the road (5.34) than at home (4.91). In actuality, his biggest issue was pitching with runners on base…

  • Bases empty: .242/.286/.417
  • Men on base: .306/.379/.506

In late June, the Rockies sent a struggling Gray down to Triple-A Albuquerque. But another big league opportunity would come soon enough for Gray, as conveyed by Deadspin’s Tom Ley

Gray didn’t stay in the minors for long, though, as injuries left the Rockies in need of another starter. He was recalled on July 14 and this time gave his team exactly what it sought, stringing together a series of strong starts and lowering his ERA by a full run by September. But then came his last start of the season against the Nationals in game 161. A victory would have kept the Rockies in the lead for NL West title, but Gray only made it through two innings and gave up five runs. The Rockies slid back into a tie with the Dodgers for the division lead, necessitating their match-up in Game 163.

As if his rough 2018 season couldn’t get any worse, Colorado decided to leave him off of their NLDS roster. This offseason, Gray sought to reinvent his game; he diligently spent time training with instructors at Driveline Baseball, whose developmental techniques are founded upon data-driven analysis.

Aside from wanting to improve his all-around game, Gray felt that training at Driveline would help him re-establish his wipeout pitch, the slider, like the training has for other players such as former teammate Adam Ottavino and Cleveland Indians starting pitcher Trevor Bauer.

Upon reviewing the data collected from Gray’s intake, the analytic gurus deemed that Gray has never actually thrown a slider; instead, he was throwing a cut fastball.

“He did not have a really good put away pitch last year,” Briend said. “There was not anything he could generate a lot of strikeouts with. Looking at the data, we discovered that he was throwing a cutter.”

Part of the problem with the cutter is that it looks similar to Gray’s fastball, making it much easier for hitters to pick up on out of the hand.

Gray’s most significant issue with the “slider” was the amount of vertical lift on the pitch. Sliders are known for their downward movement through the bottom of the hitting zone. The first slider Gray tossed at Driveline had 12 inches of vertical movement and later dropped to six-to-seven inches after some initial adjustment. By the end of his sessions at Driveline, Gray averaged between an inch-to-negative two inches of vertical break, a significant improvement from where he was upon his arrival.

Aniello Piro of Mile High Sports

Hard work is paying off for Jon Gray, who is pitching to the tune of a 3.83 ERA, 3.98 FIP, and a 3.79 xFIP. His WHIP is 1.33 (slightly below average), and he is striking out just under 9.5 batters per nine innings and walking a little bit over 3 batters per nine innings (a career high for Gray).

His slider, a pitch he specifically worked to refine/recreate at Driveline, has become his most effective offering. Hitters are swinging and missing at over 20 percent of the sliders they’ve seen from Gray this season. Their batting average and slugging percentage against the pitch is .176 and .296, respectively. These results are an improvement over the ones his cutter/slider yielded in 2018…

  • SwStr%: 19.1
  • AVG: .228
  • SLG: .392

Here’s a look at the appearance and movement on the pitch in 2019, compared to 2018 (all original video via Baseball Savant)…



In 2019, Gray’s slider is dropping on average ~1.5 inches further down than last season.

Jon Gray’s curveball has also improved by quite a bit. In generating an additional ~2.5 inches of gloveside movement on the pitch, hitters are having a harder time squaring the pitch up…

Graph: Brooks Baseball


  • Exit velocity: 86.3
  • wOBA: .250


  • Exit velocity: 83.2
  • wOBA: .184

Jon Gray’s fastball velocity has increased but the pitch hasn’t really improved at all. With that being said, it may be making his off-speed pitches more effective (greater speed differential).

  • 2018: 95.3
  • 2019: 96.3

With runners on base, Gray has maintained his composure very well, and he’s even pitched better in those situations…

  • Bases empty: .257/.333/.458
  • Men on base: .260/.316/.401

Between an uptick in fastball velocity, increased pitch movement on his slider and curveball (result of new pitch grips), and a renewal of confidence, Jon Gray has bounced back in a big way this season and is starting to pitch like the ace the Rockies had always dreamed of.

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