A Note of Caution on Aaron Sanchez

It goes without saying that Aaron Sanchez was a revelation following his callup to the Blue Jays bullpen in July 2014. The results speak for themselves: 24 outings, 33 innings, 1.09 ERA and a 28 ERA-, meaning on an adjusted basis, he allowed runs at 28% the league average. On that last metric, of the 209 MLB pitchers with 30 innings of relief in 2015, Sanchez ranked 2nd, just slightly behind Wade Davis.

Just as impressive, perhaps even more, was the raw stuff. Though we had heard reports and seen a few glimpses in Spring Training a year ago, the combination of his heavy, sinking fastball in the mid-to-upper 90s paired with a hard, hammer curveball was simply dazzling.

The combination of stuff and performance, combined with the Jays decision not to bring in established arms to bolster a bad 2014 bullpen, led to calls for Sanchez to be the set-up man or closer or even in the rotation in 2015. And now with Stroman out for the year, it appears he would have to pitch his way out the rotation in the next two weeks.

Personally, I think this is at least somewhat premature in light of control struggles in the upper minors when starting dating to the second half of 2013 and the lack of a third pitch, but I'm not going to (re)litigate the matter here. Rather, I want to examine three points related to Sanchez's 2014 numbers that I consider cautionary yellow flags about what is realistic to expect in 2015. All have discussed on this site over the winter at various points, but I've dug pretty digging deep to hopefully add some insight.

Batted Ball Data

The biggest reason for Sanchez' success was how successful he was at preventing damage on balls in play. It seemed like he generated weak ground ball after weak ground ball, in all keeping 66% of balls in play on the ground. On his 82 balls in play (excluding bunts), he had a BABIP of .160, compared to the MLB average of .299.

Inducing weak contact can allow a pitcher to sustain a low BABIP, but not nearly to that extent. For example, in the lst 20 years the lowest BABIP for a pitcher with 250 innings is .230, which is 50% of the way to league average. Further, the leaderboard of low BABIP pitchers is almost exclusively fly ball pitchers, since grounders go for hits much more often than fly balls (see table below). In the long run, even a .260 BABIP is probably unsustainable for Sanchez (for example, this spring he's at .278).

But it wasn't just ground balls on which Sanchez suppressed batted balls. The table below breaks out different batted balls for both Sanchez and the MLB average, showing frequency, batting average, and slugging percentage:

On ground balls, Sanchez suppressed batting average by 100 points, which is likely to regress much closer to league average. The performance on line drives was basically in line. But the biggest outperformance, surprisingly, was on fly balls. Sanchez allowed a home run, and everything else found a glove, meaning he outperformed by 175 point of BA and 400 points of SLG. Again, that's bound for a lot of regression.

The good news is that's there plenty of room for regression on batted balls, and for his numbers to still be very good. Sanchez' 2014 FIP- was 72, ranking 33rd of the aforementioned 209 relievers. Perhaps not truly elite as by ERA, but still excellent. And given all the ground balls (even if the percentage regresses) and resulting suppression of balls in the air, it is reasonable to expect some out performance on balls in play compared to peripherals like FIP.

Lots of Strikeouts Looking

Of the aforementioned 209 relievers with 30 innings, Sanchez ranked 104th in strikeout rate, smack dab in the middle at 22.3%. That's certainly not bad, but generally one would expect pitchers with great raw stuff to strike out more batters.

Moreover, there's an anomaly in how Sanchez achieved his strikeouts:  13 of 27, almost half, where called third strikes. MLB-wide last year, only about 25% of strikeouts were looking. Or put another way, Sanchez struck out 11.6% of all batters faced swinging compared to about 15% league average wile striking out 10.7% looking compared to league average around 5%.

Clearly, he was good at fooling and freezing batters in 2014, and this could reflect a sustainable skill. But the data suggests tome that it's probably not. The table below shows the rate of called strikes (relative to all pitches), balls, and batter swing rate by count:

With no strikes, Sanchez got a below average rate of called strikes, and with one strike he got called strikes roughly in line with league average. From no strikes to one strike, the rate of called strikes plunges, as batters are forced to be less selective and swing more often (mostly on balls in the zone, as the ball % is stable in the mid-30s). With two strikes, this is understandably even more, and batters take a called third strike less than 1 for every 20 pitches they see with two strikes. But Sanchez managed to double that rate, as batters took called third strikes 1 in every 10 pitches they saw with two strikes.

So why was that? It wasn't because he had a better ratio of called strikes/balls. He used his curveball much more often with two strikes (almost 25%) than otherwise (<10%). But the metrics on those 30 two strike curveballs are quite in line with the overall numbers: 13.3% called strikes, 33.3% balls, 53.3% swings. The big difference is that hitters were quite passive, swinging just under 55% of the time against Sanchez compared to over 60% overall. And since they took balls at roughly the league rate, it seems they were laying off pitches right on the edges.

Maybe they had scouting reports of control problems, and wanted to see if Sanchez could throw strikes under pressure and didn't want to bail him out. Maybe they were just fooled at a weird rate in a small sample, or the umpires were favourable. But MLB hitters are pretty good at adjusting, and I'm skeptical that it's a skill given that it didn't show up with zero or one strike. If Sanchez's rate of called strikeouts trends back towards league average, his overall strikeout rate would fall significantly unless he gets more via whiffs. Which leads us to...

Low Whiff Rate

Sanchez's contact rate of 84.8% (whiff rate of 15.2%), which was the 14th highest of the 209 relievers and the main reason he had so few swinging strikeouts. So was why his whiff rate is so low, especially given the quality of his stuff?

When I first became aware of this, I thought I had a theory that might explain it away: Sanchez was generating a lot weak contact early in the count, so he simply wasn't consistently getting deep enough into counts to pile up strikeouts. This could also explain the high contact rate, since the league whiff rate is only 7% with no strikes (6% first pitch) compared to 14% with two strikes. If this was the case, there's really nothing wrong.

Unfortunately, the data not only dispelled my notion, but exposed a critical issue: Sanchez was falling behind in the count too often, and therefore less often getting in position to put batter away.

Let's start with the first pitch, which is pretty critical. In 2014, when a hitter got ahead 1-0, they hit .267/.373/.420 afterwards, striking out 16% of the time. When they fell behind 0-1, they hit .221/.261/.331, with a 28% K-rate. That's a huge swing of 200 points of OPS, the difference between an All-Star and replacement player. So let's look at how Sanchez did relative to league average:

There's basically no difference in how often the ball is put in play. There is a huge difference however, in that Sanchez fell behind about 7% more and got ahead 7% less often, for a huge net 14% swing.

Did Sanchez fight his way out that hole? If a pitcher got back to 1-1 in 2014, batters only hit .233/.300/.353, compared to .280/.491/.459 if they got ahead 2-0. The same table for 1-0 pitch outcomes:

In this case, Sanchez had significantly more ball in play, and considering his dominance on them that's good. In the long run though, batters hit .331 and slugged .536 putting the ball in play 1-0, so it might not always be so good. When the ball's not in play, the 1-0 story is same: way more balls compared to league average and fewer strikes. As a result, 17% of batters Sanchez faced got to 2-0, vs. 13% for the league, a 30% difference.

I could run through the other 10 counts in a similar manner, but that would be long and tedious. Instead, below is a summary grouping the 12 counts into 5 bins along a continuum from pitcher dominant to hitter dominant, and the percentage of pitches thrown in each:

Sanchez threw about 34% of his pitches in either strong or very strong pitcher counts, compared to league average at 37%, and about 26% in strong or very strong hitter's counts compared to 22% league average. That's not a strong recipe for success, and correcting this will be critical to success as he transitions to the rotation in 2015.