Examining Matt Carpenter’s downturn

Morning, all.

We’re just over a week out from Opening Day and the parade of baseball games that actually count. Until then, however, I want to discuss one of the storylines developing down in Jupiter, which is Matt Carpenter receiving substantial reps at second base. Of course, this shouldn’t come as much of a surprise in light of the acquisition of Nolan Arenado paired with Kolten Wong’s departure.

There isn’t much debate to be had over whether Carpenter or Tommy Edman would be the better option defensively at second. The case for Carpenter was always going to revolve around his bat. Thus far, he’s hitting .291 in Spring Training. That would most likely be fine...if I were talking about his batting average. .291 is his OPS, which is extremely [choose your preferred synonym for bad]. Granted, that’s covering just 36 plate appearances with an obscenely low .063 BABIP during tuneup games with relatively little predictive power. What’s much more concerning are the overall trends for Carpenter. Consider his numbers from 2015-18 vs. 2019-20.

Those are a lot of metrics conveying a lot of bad things: less power, less getting on base, more strikeouts. Even if we give Carpenter a batting edge over Edman, it’s almost surely not large enough to outweigh Edman’s advantages elsewhere. This is to say that I presumably join most Cardinals fans in saying that Carpenter should not begin the 2021 season as a regular starter. But if St. Louis’ track record with veteran players tells us anything, it’s that they’ll probably screw this up and award Carpenter more playing time than he should be receiving at this stage in his career.

Either way, the fact of the matter is that—whether you like it or not—Carpenter is going to be a prominent part of the Cardinals’ infield plans this year. If nothing else, let’s take a look at what exactly has contributed to his offensive performance turning south the past few years.

Yes, a decline in non-contact wOBA (i.e. fewer walks and more strikeouts) isn’t helping matters, but we can see that the bulk of the problem for Carpenter arises through his post-contact numbers. His BABIP has dipped, but this can’t just be chalked up as bad luck. The xwOBA data, combining his exit velocity and launch angle figures, indicates that Carpenter hasn’t been making as much quality contact lately. This has also translated into him barreling up fewer pitches and generating less hard-hit contact.

If we check out his plate discipline metrics, we start to see a possible explanation for why (besides aging and a natural physical decline) this is happening.

Whether they’re pitches outside (O-swing) or inside (Z-swing) the strike zone, Carpenter has been swinging more frequently at everything. Understandably, this more aggressive approach has traded off with a lower rate of making contact. It’s also probably fair to assume that the less selective Carpenter is with his swings, the less productive his contact becomes.

Carpenter’s actual results (his observed wOBA rather than his expected one) were virtually identical in both timeframes when he made contact with pitches outside the zone. The major dropoff is from him not pummeling pitches in the zone as well.

There’s one additional layer I want to cover, which is that although pitchers are generally throwing the same amount of strikes to Carpenter, there are some slightly more pronounced changes in the types of pitches being thrown his way.

The pitch value numbers at the bottom of that table express how successful Carpenter has been against each pitch type, standardized on a per-100-pitch basis. When we put it all together, we find that pitchers are giving him fewer fastballs to hit and are instead throwing more offspeed and breaking pitches that he isn’t as strong against. Carpenter, meanwhile, has essentially responded to this by doubling down and swinging more often, which has hurt his BB/K ratio, contact rate, and contact quality level. Looking ahead to this season, pitch selection will be incredibly important for Carpenter, especially if he fails to regain his zapped power. If anything, the numbers suggest that his approach at the plate is heading in the wrong direction. Let’s hope a course correction is in order.