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Saying that a player is the best in the league at his position is a big deal at any position in any year, but it takes on particular importance at catcher in the AL this year. As Perez surges forward, AL catchers as a group are putting up some of the worst offensive numbers we've seen in a generation. It's not just that he's performing better than he has before -- though he is of course is -- it's that even if he wasn't, he'd have looked like a better player regardless simply by comparison.
So that brings us to an interesting place. The 2016 version of Perez is clearly the AL's only great catcher -- at least based on what we've seen so far -- in a season where many teams are struggling to find even competence. That Kansas City has a player who has performed not just acceptably, but admirably, puts them well ahead of the game, as well as making Perez a surprisingly valuable player. He's not going to win the AL Most Valuable Player Award, of course, not with guys like Mike Trout and Manny Machado and Xander Bogaerts and Josh Donaldson around, but he may be the league's most irreplacable player.
Consider these two points:
1. We're witnessing the weakest collection of hitters at catcher that the AL has seen in decades.
We can show that pretty easily by using Weighted Runs Created Plus, an all-inclusive offensive stat that sets league average as 100 and -- most importantly -- accounts for differences in eras and ballparks. For example, Michael Conforto (100 wRC+) is a league-average hitter this year, while George Springer (120 wRC+) has been 20 percentage points above average. wRC+ allows us to account for things like how much easier it was to hit in (for example) 1999 Coors Field as opposed to 2016 Petco Park.
Based on that, it's been a grim year for AL catchers. Going back to the beginning of the "live ball" era in 1920, we have 97 seasons on record. AL catchers so far this year, even with Perez, well, let's just show the three lowest marks:
95. 2016 -- 78 wRC+
96. 1965 -- 77 wRC+
97. 1942 -- 70 wRC+
As usually reliable performers like Yan Gomes (49 wRC+), Russell Martin (76 wRC+), and Dioner Navarro (63 wRC+) struggle to get back to their usual levels, and other teams struggle to fill the spot at all, the overall performance level drops. That makes any elite performer look even better.
2. Perez is head and shoulders above the competition.
As we noted, Perez's 130 wRC+ means that he's 30 percentage points better than league-average. Of course, that's above all hitters, not just catchers, and no other position has anything like the kind of gap (25 points) that Perez has over Matt Wieters, who sits in second with a 105 wRC+. For example, Machado is one of five AL shortstops with wRC+ marks above 122, and his lead over second-place Bogaerts is just 12 points. At second base Jose Altuve (161 wRC+) holds a similar lead over Robinson Cano (148 wRC+).
If the Royals were to go from Perez to an AL-average catcher, they'd be going from a .300/.331/.536 line to a .225/.291/.374 mark -- if, that is, they could find an average catcher, which many teams can't.
So what's behind this sudden offensive improvement from Perez?
Less contact may not be a bad thing...
It's not that Perez wants to strike out, of course. But a look at his plate discipline statistics shows what's really going on here. Despite a preseason pledge to improve his discipline, Perez isn't really swinging at more or fewer pitches. He is, however, making contact with fewer pitches outside the zone, down from 71 percent to 64 percent. That's a big deal; as we showed last offfseason, making contact on bad pitches that can't be driven is a huge help for the pitcher. Missing those and avoiding the generally poor contact that follows is a plus.
...as it's helped him hit the ball harder…
As we noted above, Perez's overall exit velocity is up nearly three miles per hour, and less contact outside the zone is part of that. Over the past two years, when making contact outside the zone, his exit velocity has been 84.5 mph. Inside the zone, it's 91.9 mph. Like every other hitter, there's a rough difference of about seven mph on contact in and outside of the zone, and that matters. Over that time, Perez hits .242 with a .343 slugging outside the zone, and .314 with a .523 slugging inside it.
...and at a better launch angle.
Likely in no small part because Perez isn't hitting the ball outside the zone as much, his launch angle has improved as well, going from 13.3 degrees to 18.3 degrees. In other words, his ground-ball rate has dropped from 42 percent to 28 percent, and that's great for him -- Perez hits just .218 on grounders, not unexpectedly.
For years, Perez has been a bit divisive, as he's paired a yearly increase in home runs with a yearly decrease in on base percentage, which has mostly muted his hitting value. So far this year, he's managed to have both. At the same time, AL catchers have fallen apart. The result is that well Perez isn't and won't be the MVP, he's extremely valuable. After all, the Royals have what no other AL team has this year, and that's a catcher who's a plus on both sides of the ball. It's not a small thing.