Gauging The Value Of Starter Sonny Gray

After a less than stellar 2015 season, Dave Dombrowski and the Boston Red Sox are in need of a front-line pitcher. The free agent market offers David Price, Johnny Cueto, and Zack Greinke, among others. Shane Liss-Riordan takes a look at starter Sonny Gray’s numbers to determine if he’s worth the giant haul needed to acquire him.

It’s no secret the Red Sox need starting pitching. Red Sox starters this year had a 4.39 ERA, seventh worst in baseball. A solid top-of-the-rotation starter would go a long way to helping this team get back to the playoffs in 2016. Last offseason the attention was on Cole Hamels. This year one name that keeps coming up is Sonny Gray.

There’s a lot to like about Gray. He finished 2015 with a 2.73 ERA over 208 innings pitched. He’s a Cy Young candidate in the American League this year. He’s young, only 25, the same age as Jackie Bradley Jr. This offseason many of the top free agent pitchers David Price, Johnny Cueto, Zack Greinke, and Jordan Zimmermann are going to command mega-deals. In contrast, Gray still has a year of team control, followed by three arbitration years. David Ortiz even ranked him as one of the five toughest pitchers he’s faced in his career on a list that included Pedro Martinez, Mariano Rivera, Mike Mussina, and Marlins reliever Carter Capps. He represents the kind of young, inexpensive ace that teams try to build around. Rarely are these types available on the trade market. However, since he plays for Billy Beane, his value will at least be tested on the trade market. The Red Sox, who possess the young talent necessary to make a serious offer, have to make a run at Gray this winter, right?

Not so fast.

We would expect a pitcher with an ERA as good as Gray’s this year to rank near the top in K% and BB%. However, Gray’s K% was 20.3%, barely above the league average of 20%; and his BB% of 7.1% was worse than the average mark of 6.5%. Gray also doesn’t produce a lot of swings and misses. Brian Bannister, recently hired by the Red Sox for pitching analysis, went so far as to say that Z-Cont% (the batter’s contact percentage when he swings at a pitch inside the strike-zone) is the most important stat for predicting future success for pitchers. It makes sense: if a pitcher generates less contact, he gives up fewer balls in play, which means fewer hits. League average is 87%; Gray this year was 88.4%. While that may not seem like a substantial difference, the difference between a top-20 pitcher and a bottom-20 pitcher is only 4%: 85% vs. 89%. So how did a pitcher who had a higher than average contact rate, who struck out an average number of batters and walked more than average, post an ERA of 2.73?

To get an idea of what sort of seasons other pitchers have had with strikeout and walk percentages similar to Gray, I made a list of pitchers in the past twenty years that were within +/- 0.5% of Gray’s 20.3 K%, and within +/- 0.3% of Gray’s 7.1 BB%. The list contained nineteen pitchers, including such names as Ivan Nova, Gavin Floyd, and John Danks. The only exceptional season on the list was Brandon Webb’s 2007, a year in which he went 18-10 with a 3.01 ERA and earned second place in the NL Cy Young voting. But that year Webb had a GB% of 61.8%, much higher than the league average of about 44%. Overall, the group of 19 pitchers had an average ERA of 3.84, a far cry from Gray’s 2.73. Interestingly, Gray’s SIERA this year was 3.80, almost identical to the average ERA of 3.84. This suggests that Gray’s SIERA is a much better indicator of how well he has actually pitched.

Is it Gray’s ability to get ground balls, like Webb, that explains his success? The league GB% is about 44%. Gray was well above that with 52.7% last year (and sports a career percentage of 54.2%). But he was still significantly below pitchers such as Dallas Keuchel in 2015 (61.7%), Tim Hudson in 2010 (64.1%), and Derek Lowe in 2002 (66.8%). Let’s look at pitchers since 2002 (the first year for which batted-ball breakdowns are available) with ground ball rates similar to Gray. Eliminating the elite ground ball pitchers with GB% higher than 60%, and the superior strikeout pitchers with Z-Cont% and K% much better than Gray (Z-Cont% less than 87% or K% greater than 21%), one gets a list of 85 pitchers. The median ERA of pitchers on this list is an unspectacular 4.00, which doesn’t look anything like Gray’s 2015 ERA of 2.73. Again, Gray’s SIERA, 3.80, is a much closer match.

If Gray’s success was not because of great strikeout and walk percentages, and it wasn’t because of his tendency to produce a large number of ground balls, then what is it?

When the ball is put in play, the pitcher is known to have very little to do with the outcome. The velocity of the contact depends largely on the batter. We should expect most pitchers therefore to have a LD% close to league average. An average LD% is 21%, while Gray this year recorded a LD% of 16.6%, meaning he somehow allowed far fewer line-drives, which typically fall for hits because of their velocity, than normal; in fact, his LD% was actually the fourth lowest in baseball. Similarly, when we look at BABIP, we find that Gray posted a .255 BABIP, the fifth lowest in baseball, compared to a league average of .300. When Gray allowed the ball to be put in play, outs were recorded far more often than normal. Was that because of park factors, superior defense, some unique skill that Gray has, or just plain luck?

Since 2010, there have been 40 pitchers who recorded seasons with a BABIP lower than .265 and an ERA below 3.30. On average, in the following year, their ERAs increased by 0.87, almost a full run. Adding this mark to Gray’s 2015 ERA of 2.73 brings him to 3.60, decent but not that of a Cy Young candidate. Additionally, this ERA of 3.60 is very similar to Gray’s 2015 SIERA of 3.80.

“Ideally, everyone would love to get a top-of-the-rotation starter,” Dave Dombrowski said at the end of the season. “They’re not that easy to find. And you have to be careful that, when you acquire that person, they’re legitimately a top-of-the-rotation starter – not thought of as that but really not.”

Sonny Gray’s 2015 peripherals suggest the he is the latter – a good pitcher, but not someone worth the huge package of young talent that Billy Beane would surely demand.

Follow Shane on Twitter @slissriordan.