Over- and Under-Achievers, Alleged

Chris Davis has been playing out of his mind. In a different sort of way, Ike Davis was playing out of his mind, too, before getting demoted. If you already knew those things, you might not need to read the rest of this post. But things do get a little more complex.

We’re to the point, now, where a lot of players have amassed fairly significant sample sizes of regular-season data. Manny Machado, for example, has 323 plate appearances, and that makes for an awful lot of repetitions. What players have done so far should tell us something about what they’re going to do going forward. After all, the most recent past is the most important. But we also can’t yet discard the less recent past. This is the whole point behind rest-of-season projections, and we’ve got two of them right here in ZiPS and Steamer.

Those two projection systems begin with an idea. Then, over the course of the season, they update themselves based on the new information. They are, basically, performance + regression, and collectively they give the best idea of what could take place in the coming weeks and months. They might take a while to identify changes in true talent, but they’re conservative in the way that human observers tend to be over-aggressive so it’s not like that counts as a flaw.

I found myself wondering about over-achievers and under-achievers. I took that to mean players who are over-shooting and under-shooting their rest-of-season projections. It’s a pretty simple idea, and I looked only at position players (with at least 150 plate appearances), since pitchers get tricky when you try to decide between FIP and xFIP. The short of it: I blended ZiPS wOBA and Steamer wOBA. I compared that projection to 2013 player performance so far, and found the difference. Following, extremes, in the form of a couple top-ten lists.

Top 10 Under-Achievers

Player	Team	2013 wOBA	RoS wOBA	Difference
Ike Davis	Mets	0.225	0.319	-0.094
Danny Espinosa	Nationals	0.205	0.296	-0.091
Jeff Keppinger	White Sox	0.220	0.301	-0.081
Matt Kemp	Dodgers	0.278	0.353	-0.075
Steve Lombardozzi	Nationals	0.221	0.291	-0.070
Mike Moustakas	Royals	0.242	0.311	-0.069
Alex Avila	Tigers	0.256	0.322	-0.066
Ryan Flaherty	Orioles	0.212	0.275	-0.063
Dustin Ackley	Mariners	0.237	0.299	-0.062
B.J. Upton	Braves	0.258	0.319	-0.061

Nobody ought to surprise you. This post isn’t going to be surprising. Nobody’s been a bigger under-achiever than Ike Davis, and that’s essentially why he’s presently back in the minors, trying to figure his business out. You can also see that we’re selecting for some injury excuses. Espinosa was playing hurt, which easily could’ve contributed to his terrible performance. Kemp, too, might’ve been playing hurt, and his numbers are disastrous across the board. When a player under-performs, it’s easier to blame injury than the player himself, so the availability of excuses is always comforting.

None of these players, at present, look like a great bet. But all of these players have been struggling, and struggling players don’t look like great bets, because they’re making too many outs and that’s difficult to ignore. A normal, healthy player will go through slumps, and during those slumps he’ll usually look bad, even though nothing is seriously wrong. We think we’re great at telling the difference between a normal slump and a miserable, meaningful one. We’re not, really. We’re at least no better than math.

Top 10 Over-Achievers

Player	Team	2013 wOBA	RoS wOBA	Difference
Chris Davis	Orioles	0.459	0.365	0.095
Adam Lind	Blue Jays	0.417	0.347	0.071
Carlos Gomez	Brewers	0.398	0.332	0.067
Jean Segura	Brewers	0.382	0.329	0.054
Michael Cuddyer	Rockies	0.419	0.366	0.054
Josh Donaldson	Athletics	0.378	0.326	0.052
Everth Cabrera	Padres	0.354	0.303	0.052
Jhonny Peralta	Tigers	0.375	0.325	0.051
Bryce Harper	Nationals	0.411	0.362	0.050
Didi Gregorius	Diamondbacks	0.356	0.307	0.049

Yeah, so, you could’ve guessed that. Chris Davis is having one of the greatest offensive seasons of all time, and the expectation is that that’s going to slow down. But it’s important to note that even the rest-of-season projection leaves Davis as a quality player, and a better hitter than he was a season ago. Davis is a mystery and he’s fascinating and he’s incredible with his effortless strength, but it’s no crazier to think he’ll slow down than it is to think he’ll keep this up. He still projects for a higher wOBA than Bryce Harper, which might touch off an argument in the comments.

Lind is a month from 30 and he’s hitting well for the first time since 2009. Gomez is challenging Miguel Cabrera’s isolated slugging percentage, but he’s also had a lot of balls in play end up as hits. It’s interesting to note the shortstops. I was in charge of the shortstop positional power ranking before the year, and the Brewers were in the bottom half with the Padres in a tie. The Tigers were right in the middle. The Diamondbacks were tied for 24th. Littler things haven’t gone quite as expected, which is why some bigger things haven’t gone quite as expected, in turn.

Nothing in there is going to blow you away, but each of these players allows for a conversation. Who’s going to keep it up? Who’s going to play to the projections? Why? How much better are we than the projection systems, in isolated cases? How much sooner can we tell that a change in performance is real?

Just for fun, I also darted over to our projected standings page, and compared team winning percentage to rest-of-season projected winning percentage, based on our depth charts. Understand, of course, that these depth charts can’t foresee future trades around the deadline, so we can only project based on rosters and injury information.

Top Five Under-Achievers

Team	2013 W%	RoS W%	Difference
Angels	0.435	0.547	-0.112
Dodgers	0.427	0.524	-0.097
Marlins	0.309	0.392	-0.083
Brewers	0.412	0.488	-0.076
Cubs	0.418	0.491	-0.073

Top Five Over-Achievers

Team	2013 W%	RoS W%	Difference
Cardinals	0.638	0.532	0.106
Pirates	0.594	0.502	0.092
Reds	0.600	0.515	0.085
Orioles	0.571	0.493	0.078
Athletics	0.592	0.516	0.076

The Angels are projected to be the third-best team in baseball the rest of the way. Yet, they’re projected to end up with 81 wins. The Cardinals, Pirates, and Reds are all supposedly in line for regression, but they’re projected for 94, 88, and 89 wins, respectively. That would put the Pirates and Reds in line for a one-game playoff, since no other team in the National League is projected to end up with more than 83 wins, excluding the division champs. One notes the picture in the NL West. There’s a division where one trade could make a significant difference.

Maybe, you learned a lot from reading this post. If not, you already have a pretty good grasp on baseball and its statistics, and on the principle of regression. Perhaps a better grasp than you thought.