The day Bryce Harper scared major league pitchers

Bryce Harper, the Washington Nationals' 22-year-old right fielder, is having an unbelievable offensive season. That's incredibly obvious though and not the point of this article. Still, it's fun to mention some numbers. Like this one: In under 70 games, he's put up +5.1 fWAR, and is poised to surpass the +10 fWAR mark for the year if he can keep things up. Only Alex Rodriguez, Barry Bonds, and Mike Trout have posted seasons at or surpassing that mark since 2000.

We're seeing performance like the prime-hitting career of Barry Bonds, in other words. Harper's video-game batting stats are the return on what some fans might consider his ordainment as "The Chosen One" when he was 16. But it hasn't always been that way, at least if the attitudes of opposing pitchers are the metric.

Recently--and right before he was placed on the DL--we saw how pitchers were approaching Ryan Zimmerman using Rob Arthur's zone distance stat. Arthur surmised that when a hurler pitches to a batter, pitch distance from the center of the zone indicates not just how the batter has performed, but how he may perform in the future. The closer to the middle of the zone, the less afraid a pitcher was of a hitter doing damage.

It was clear pitchers started to attack Zimmerman more this season from the get-go. We didn't know it at the time, but that approach would be validated through the Face of the Franchise's poor offensive performance. Only once an injury became apparent did the Nationals take action to get their slugger healed and, hopefully, feared for the stretch run.

With Harper's exceptional numbers this year, I wanted to know: just when did dudes start working away from him?  Did they start working away from him, or was he respected--to the extent we can apply that term to zone distance--such that pitchers had always stayed away?

We have an answer. But for context, here are the total number of pitches Harper saw/has seen for the following years:

Right. About 7,000 career pitches seen, with 2012 being the most for his career. Harper was hurt in both 2013 and 2014 (accounting for the lower pitches seen), and these injuries feature fairly prominently in this article, so keep them in mind.

And now his zone distance graph for his career. The x-axis represents number of pitches, corresponding with the "running total" for each season above. The y-axis represents in feet the distance of each pitch from the center of Harper's zone:

A couple things jump out. First, about 1/3 to 1/2 way through the 2013 campaign (around pitch 3,000), the opposition started to venture closer and closer to the center of Harper's strike zone.  Remember Harper hurt his knee that year--how can we forget--and came back in July. That's about the same time pitchers started to get more aggressive in the strike zone, betting that Harper wasn't the same guy he was before the injury.

Harper was the same guy, though: his wRC+ values in July, August, and September/October 2013 were 118, 140, and 90. Okay, so September was a bit of a downer. But with those numbers, it's surprising pitchers continued to attack him.

Second, around pitch 4,600, opposing hurlers decided that they'd tempted fate enough, and started working further away from Harper's turbo zone. This zoomed-in version of the above graph shows the beginning of what has been an uptick in zone distance to this day:

Using my rudimentary math skills and questionable baseball judgment, I figured it was possible to identify (more or less) the exact day and pitch that Harper made pitchers tuck tail and run. Recall that like 2013, Harper got hurt in 2014; on April 25, he tore the UCL in his left thumb. The above graph suggests attitudes changed towards the Las Vegas lefty somewhere between pitch 4,550 and 4,600.

Now wait for it: Harper's 2014 injury occurred immediately after pitch 4,571--just about EXACTLY the same time pitchers started to go away from him. Pitch 4,571 of Harper's young career, delivered by the San Diego Padres' Robbie Erlin on a 3-2 count in the bottom of the third, saw a blistering triple to right clear the bases:

This is the date major league pitchers had their Sugar Ray Leonard-Roberto Durán II moment: no más. Since that time, the best of the best have continued to work Harper further from the center of his zone. Enough was enough.

Which is really interesting to me. After Harper returned from injury in 2014, pitchers had made up their minds not to challenge the precocious young slugger. That's the opposite of what they did in 2013.  All injuries affect hitting ability to some degree, but given Harper's thumb ligament tear, it's a bit surprising how the opposition generally pitched him in the following months. And as this season shows us, pitching further from Harper's zone center definitely hasn't helped.

There's a complimentary point to this trend. Not only have Harper's power numbers been bonkers, but he's also disciplined enough to take walks when given to him. Pitchers can't stray too far from the zone like they can with, say, Chris Davis.

How much further will the bad guys work Harper away? And for how long? Perhaps with the right-fielder's recent maladies, pitchers will delicately begin to work closer to the center of his zone. But the zone distance graph above suggests they may know better.

Thanks to Baseball Savant and Rob Arthur for stats, info, and help.