Bryce Harper is a (nearly) unrestricted free agent. He is newly 26 years old. He is projected, by Steamer, to be baseball’s second-best hitter next season. According to reports, he’s already turned down a contract offer worth $300 million. According to MLB Trade Rumors, he might end up with a contract worth more than $400 million. We’ve been anticipating this offseason for a while. Harper has been a household name for longer than I can remember, and as the cherry on top here, he’s represented by Scott Boras. Boras will push for some kind of contract record. I expect he’s going to be successful. Harper’s a core player in the prime of his life, and there’s more money in baseball than ever before.

Earlier this morning, almost by accident, I noticed that Harper was worse than Mitch Haniger in 2018, by 1.1 wins above replacement.

The point is not that Haniger is better than Harper is. Age is on Harper’s side. Talent is on Harper’s side. Track record is on Harper’s side. While I don’t know how much of a believer I am in the concept of measurable ceilings, we sort of know what Harper’s ceiling is, because we saw it in 2015. He was unbelievable. He hasn’t become as consistent as one would like, but Harper hits for power and he draws a boatload of walks. He just played in a career-high 159 games.

The Haniger thing got me looking closer, though. And in Harper’s otherwise good-enough contract season, he raised some questions about his defense. We still don’t focus that much on defense when we’re talking about sluggers. But teams don’t ignore it. Teams interested in Harper will have to figure out what happened.

Bryce Harper, this past season, played a bunch of right field. He also spent plenty of time covering ground in center field. You’re correct if you’re already saying in your head that playing center comes with a greater degree of difficulty. And it’s a good thing, just in general, that the Nationals considered Harper center-field capable. But according to Defensive Runs Saved, Harper finished the year an incredible 26 runs worse than average. According to Ultimate Zone Rating, he finished the year a slightly less incredible 14 runs worse than average. This after a perfectly fine 2017.

We have Statcast information now. This is the 2018 Outs Above Average leaderboard. Scroll all the way down and you find Harper at -12, somehow around names like Derek Dietrich and Trey Mancini. A year ago, Harper wound up at -5, meaning he got worse by seven outs. That’s tied for the fourth-biggest drop among outfielders. And this is only measuring positioning and range. Both DRS and UZR agree that Harper’s arm was considerably less valuable.

I’m going to show you some tables. I looked at every outfielder who played at least 500 innings in both 2017 and 2018. For each season, I calculated DRS per 1000 innings, UZR per 1000 innings, and a combo per 1000 innings, which is just the average of the two. First, here are the ten biggest drops in DRS/1000:

Harper’s right there by the bottom. Here are the ten biggest drops in UZR/1000:

Biggest Outfield Defense Declines Player 2017 UZR/1000 2018 UZR/1000 Change Odubel Herrera 7 -9 -15 Bryce Harper 3 -11 -14 Yasiel Puig 10 -4 -14 Steven Souza Jr. 3 -9 -12 Aaron Hicks 10 1 -10 Tommy Pham 9 0 -10 Austin Jackson -5 -14 -9 Charlie Blackmon -1 -9 -9 Joey Rickard 9 1 -8 Gerardo Parra 10 2 -8

So, unsurprisingly, this is what it looks like when you put the two together:

Biggest Outfield Defense Declines Player 2017 Combo/1000 2018 Combo/1000 Change Bryce Harper 4 -15 -19 Aaron Hicks 16 -1 -17 Odubel Herrera 5 -9 -14 Charlie Blackmon -2 -15 -13 Austin Jackson -4 -17 -13 Joey Rickard 13 2 -11 Yasiel Puig 12 1 -11 Tommy Pham 10 -1 -11 Guillermo Heredia 2 -9 -11 Stephen Piscotty 7 -2 -9

All these are are numbers, and defensive numbers don’t work like offensive numbers do. When a batter hits a single, it’s easy to record. 1-for-1. Base hit. On the defensive side, you start talking about probabilities and estimates and it all gets complicated very quickly. It’s absolutely true that defensive numbers still have a ways to evolve. But metrics like DRS, and UZR, and Outs Above Average — they’re designed in the ways you’d want such metrics to be designed. They provide information, based on complex math. For one reason or another, the existing metrics agree that Bryce Harper’s outfield defense just tanked.

It’s not clear why! I mean, it’s clear he made fewer plays, but 2018 Harper didn’t land on the disabled list. He, again, only recently turned 26. He stole 13 bases, after stealing just four the previous season. And, importantly, Harper’s sprint speed didn’t budge. It would appear he can still move like he used to. Yet the results are the results. Here’s one Harper misplay where he comes off looking clumsy:

And here’s a play where he maybe just didn’t get a good read or first step:

A quick read of Statcast suggests Harper had some particular trouble with the easier plays, as opposed to the more difficult ones. Harper missed five of 23 so-called “1 Star” plays, which looks dreadful. That was one of the very worst marks in the league. Harper was nearly as good on “2 Star” plays. I’m not going to dig in too deeply because that would be a whole other project. Basically, I don’t know whether this is a good thing or a bad thing.

But what matters most now isn’t what Harper did — it’s what Harper could be expected to do. I’ve run some numbers to try to be helpful. In terms of Outs Above Average, I looked at the players who had the biggest declines from 2016 to 2017, and then I examined how they did in 2018. On average, the players gained back a third of the ground that they lost. That’s one data point.

I also looked at DRS and UZR going all the way back to 2003. I took all the players who played in the outfield enough in three consecutive seasons, and then I isolated the players with the biggest declines between year one and year two. In year three, the players who declined the most in terms of DRS gained back a little more than a third of the loss. The players who declined the most in terms of UZR gained back a little less than a third of the loss. It’s almost exactly a third if you average DRS and UZR. To put it simply, the numbers are in the same ballpark: On average, based on recent history, when an outfield defender has gotten significantly worse between seasons, then the following season, that defender has rebounded by about 33%. Two-thirds of the decline has been real.

That’s the average. That’s not the case for every individual player. So this is where the Harper sweepstakes gets more complicated. He’s still young, and he seems healthy, and he can still apparently sprint like he used to. You might be inclined to think his defense could rebound almost all the way. Perhaps in 2018 it was more just a problem of focus. But then, can you overcome a problem of focus, in that case? Was the problem something else? Has something meaningfully gotten worse about Harper’s throwing arm? If the average is that a declining outfield defender rebounds by a third or so, then with Harper, do you take the over or the under? All of this is far less important than the matter of Harper’s bat, but the defense counts. Especially when you’re thinking about signing a guy for at least the next decade.

Harper hadn’t rated as a terrible defender before. That’s good. That might suggest that 2018 was an anomaly. Heaven knows that’s how Boras will spin it. But teams want to know what the future will hold, and this is almost certain to be the biggest contract in baseball history, once it gets signed. Teams are going to try to figure out what on earth happened. Because whoever signs Harper will be signing more than just a hitter. Whether playing offense or defense, every out has value.