So let's discuss Ryan Zimmerman. I'm not going to waste time with a long lead-in. He was terrible last year. He's great so far this year. Is this real or not? Is this sustainable or a flash in the pan?
I could go through a bunch of numbers but I want to try to do this systematically. Think about how I'd answer the question before looking at the numbers. Ok, well the first thing I would do is try to determine if Ryan has just been lucky or not. Generally that means looking at BABIP and HR/FB rates. It's not that a person can't control these things but there are certain historic limits to these numbers. In the past 5 years the highest BABIP seen was Chris Johnson's .394 in 2013. The highest HR/FB rate was Nelson Cruz 30.3% in 2015. So if Zimm is beating either of these he almost HAS to come back down. Let's check...
BABIP : .448
HR/FB : 40.7%
Ok he's been lucky. But come on. He's on pace to hit .420 with 70 home runs. It would be crazy if I didn't find him to be lucky. So congratulations we've determined he shouldn't have the best offensive season in the history of the game.
The next question I'd try to answer is how lucky is he? That's harder question. What I would probably look at next is trying to see if he's hitting better. If he's not then he's probably getting real lucky, if he is there's probably something "real" behind this. By hitting better I mean he would (1) hit fewer balls softer / more balls harder*, (2) Hit more line drives,** (3) swing and miss fewer times. Those are all things I'd like to see. But better than what? Better than last year? That only tells us that he's not terrible. Let's see how he compares not only to 2016 but to "peak Zimm", 2009/2010 Zimm.
2009: 12.4% / 35.8%
2010: 14.8% / 40.0%
2016: 15.2% / 34.7%
2017: 10.1% / 40.6%
Zimm is hitting it, at least in April, as well as he ever has. He's hitting it hard. He's hitting it on a line. He's swinging and missing more than "peak Zimm" but that could be a necessary trade-off to the harder swings. It isn't surprising to see a very good statistical month given this.
But what you might have noticed is that 2016 doesn't look too far off "peak Zim" either. Maybe too many swings and misses but he was hitting it hard and while not as line drivey as 2017, just as line drivey as 2009 and 2010. Remember what we were told about Zimm last year, though. He was hitting the ball hard but was hitting the ball too much into the ground. Was that actually a problem? Did he change that?
Yes. Yes he did hit a lot of ground balls. Yes he did change that. It's not necessarily true that if you hit a lot of groundballs that's bad, though. So let's take a look at that BABIP from last year.
2016 : .248
That's near the bottom of the usual range. So there was an element of bad luck likely there last year.
But back to the question at hand. Is what Zimm is doing real, is it sustainable? The answer to the first question is yes, I think so (with the caveat of we're only talking about a month here). Like I said he is hitting hard and square. If I take a look at the 2016 leaderboard and come up with a quick and dirty "Hard and Square" stat (say (hard% - soft%) + LD%) you see the names you want to see in that Top 10. Freeman, Carpenter, Ortiz, Votto, Cabrera, Trout, JD Martinez, Corey Seager, Justin Turner. The bottom is filled with disappointments - Iglesias, Heyward, Alcides Escobar, Schoop, Panik, Pillar. It's not a perfect "Up Here = Stardom, Down There = Garbage" but it's close. So while .420 70 HR pace is not sustainable, I don't think that's what you're asking. If he keeps hitting like he is, a fair expectation would be something like .310 and a 28 HR pace.*** What would be the best case if luck never went away just became reasonable season long most lucky? Oh like finishing the season .370+ with 50+ homers. Worst case if luck spun around to worst reasonable while still hitting like this? Like .250 with 25 homers.
The sustainable question, "can keep hitting like this" - not "are the stats real", is a big I don't know. Certainly players can hit for a season generally like Zimm is now. But can Zimm do it? Or is this a one month mirage? He hasn't really hit this well since the "peak Zimm" years and even then he wasn't like this. "Peak Zimm" was a patient hitter who worked a fair amount of walks and saw a lot of pitches. 2017 Zimm is an aggressive hitter who attacks the count early. He's a different animal. So I can't simply say - this is how he hits when he's healthy because he's never hit like this before. There's something more here and the question is whether that is something that can last a season. One thing that may happen is that as teams realize they can't pitch to Zimm as they did last year, they may start throwing it down and out a lot more. What happens then? Does Zimm pivot back to patience? Or will he swing and miss at those trying to keep up aggressiveness? Or maybe counter with fewer homers but more singles and doubles to the opposite field?
My guess is we'll know how a healthy last 60% of the year will play out by mid June. At that point he'll have 4 rounds vs the Phillies, and 3 vs the Mets and Braves. If they are able to make exploitable adjustments you figure they'd do it by then. If he's still hitting real well by mid June, I'd buy on Zimm finishing the season strong.
*Hard balls good! Soft balls bad!
** Line drives better than flyballs or ground balls.
*** That would be from here on out so his actual final numbers would be more like .335 33 homers