The Right “Stuff”: A new baseball analytic

Roberto Osuna

Roberto Osuna

For decades, we’ve heard baseball play-by-play announcers laud the game’s Rembrandts for having “great stuff” during their most effective outings on the mound. But in this data-driven era of analytics, that sounds like a very abstract term.  So just how do you quantify a pitcher’s “stuff”?

Ergonomist and McMaster University alumnus Mike Sonne (also featured in my most recent blog) has developed a metric aptly named “Stuff” to attempt to do exactly that.

“The idea is essentially three parts – how much velocity can a pitcher generate, how much change in velocity a pitcher generate, and then how much space can they cover between their pitches,” said Sonne, who utilizes Fangraphs PITCHF/x data to come up with a measurement.

“So I can go in and I can look at all of those data and I put them all in a spreadsheet, and I run some calculations, and it puts out a number, and we do a ranking based off of that,” Sonne said.

As you might expect, the best pitchers in baseball have the best “Stuff”. This season, the Cubs’ Jake Arrieta is tops among starters at 2.38, followed by Noah Syndergaard, Stephen Strasburg and Clayton Kershaw.  The Blue Jays’ Aaron Sanchez ranks 7th at 1.62.

Among relievers, the Cubs’ Aroldis Chapman is best at 2.48. The best Blue Jays reliever is Joe Biagini at 1.61, whose number is better than 96 per cent of 7,000 pitchers Sonne has studied.  It might help explain why Toronto made him a Rule 5 draft pick and have kept him on their roster all season, allowing him to become an important part of their bullpen.

Not surprisingly, the Cubs are tops in team “Stuff” rankings for both starters and relievers. The Blue Jays bullpen, which struggled earlier in the season, ranks 11th among MLB teams. However, the Jays are dead last in “Stuff” when it comes to their starters – Sonne attributes this mostly to slow-throwing knuckleballer RA Dickey, who skews their calculation.  Still, it’s curious considering the Jays’ starters have the best rotation ERA in the American League and 4th best in the majors at 3.67.

There’s another question here — is too much “Stuff” a bad thing? Take former Jays reliever Drew Storen, who posted an ugly 6.21  ERA before being dealt to Seattle last month.  A big part of his problems this year surrounded a slider that moved too much and was so far out of the strike zone hitters were able to lay off and work favourable counts.  Not surprisingly in Storen’s case, his “Stuff” varied wildly.

“There’d be weeks where his Stuff was awesome, and weeks where it was just absolutely terrible,” Sonne said, adding “Stuff” isn’t exactly a parabolic metric. However, a pitcher who registers a lot of “Stuff” that is inconsistent and uncontrollable should raise serious red flags for teams.

“The Stuff metric as an injury prevention tool is also something that I’m trying to look into,” said Sonne, who highlights the fact that the A’s Chris Bassett and the Angels’ Garrett Richards had the most “Stuff” at the start of the season. Bassitt underwent Tommy John surgery in early May, while Richards started pursuing alternative therapies just days later in an attempt to avoid it.

“All of them had control issues, all of them had great Stuff,” said Sonne. “The theory is that if you have great Stuff but you can’t harness it, it’s harder on your arm. There’s a whole  motor control thing on that we’re still exploring.”

Further to his point, Sonne noted that Blue Jays hurlers Brett Cecil and Marco Estrada both saw significant declines in their “Stuff” numbers in the time periods just prior to their respective injuries coming to light this season.

Examining this data has also led Sonne to other discoveries as well – ones which could change how pitchers and organizations think and approach the game.

“Veritcal movement gets you more swinging strikes, while horizontal movement gets you a lower batting average,” said Sonne, who thinks the concept of “pitching to contact” is falling by the wayside.

“If your arsenal of pitches generates swinging strikes, generates a lot of strikeouts, you’re also going to get that bad contact a lot with it.”

Again, if you want to learn more, Sonne plans to attend the next Toronto Pitch Talks session on September 8th ( )



Sonne’s latest “stuff” rankings: