O.M.G., the Phillies are finally back to .500! Cole Hamels is back on track! Cliff Lee is cruising! And don't get me started on Dom Brown!
Wait, wait, wait, hold on a second. Let's roll this back a bit. One of those players is not like the others. One of those players is significantly younger and less proven. One of those players has performed at a pace that is thoroughly unsustainable. One of those players is Domonic Brown.
Now, before I sound like a downer, I do want to say that what Brown has done in the past few weeks has been absurd. In his past 16 games (yes, beyond the 12 that everyone's been raving about), he has a special .381/.400/1.000 BA/OBP/SLG line with 11 HR, 15 R, 24 RBI, and 3 SB. This streak has vaulted him to top ranks in MLB in home runs (2nd), RBI (9th), and slugging percentage (7th). But I was listening to the radio the other day and people were calling in and saying that he would be batting .300 with 30 HR and 70 RBI by the All-Star Break. That's ridiculous, and we all know it.
Well, first of all, he was hitting just .243/.282/.414 for the first 44 games of the year, and has 40% of his hits, 60% of his home runs, and 50% of his runs and RBI in just 27% of his games. He had never had better than a .245 BA, .333 OBP, or .396 SLG in any of his previous seasons in the league (admittedly, less than a full season's worth). So would you rather believe 16 games, or 140?
OK, let's get a little more sabermetric. One strong indicator of luck is home-run-per-fly-ball-percentage (HR/FB%), or the percentage of fly balls that end up being home runs. Given how small changes in contact angle off the bat can dramatically affect batted ball trajectory, there's a lot of potential randomness in how many of a player's fly balls become outs versus doubles versus homers. While players generally have somewhat consistent HR/FB% over their careers (Ryan Howard has averaged about 28% while Jimmy Rollins has averaged 8%), there is also some variability that can occur around those averages (Howard has ranged between 21% and 39%, while Rollins has ranged between 4% and 11%). Brown's previous three seasons' HR/FB% were 13.3, 9.4, and 9.8, but this year it's 31.6. For reference, no one in the league has had a rate that high for an entire season since Howard himself in 2008. Are you really willing to claim that Dom Brown went from almost-traded-for-Alfonso-Soriano to Ryan-Howard-in-his-prime in a third of a season?
Not that I feel like this is the biggest point, but it's also worth pointing out that while Brown never really got it going offensively in his previous years, he did at least have a decent eye at the plate, walking an above-average 10% of the time. This year, he's walking half as much, and is striking out more, which does not portend continued success. Just as indicative of his lack of patience is that he has increased his swing rate by 8% over his career average, which could hurt him once pitchers eventually figure out that fastballs just aren't going to cut it. (Maybe a cutter will, eh?)
I would love to see Brown do well after all he's been through in the early stages of his career, but I'm not going to get carried away with the hyperbole. I think he ends up with a line that looks something like .265/.330/.500 with 30 HR, 85 R, and 105 RBI, which would be almost an exact midpoint between Howard's 2010-11 seasons. Yes, that's huge for our lineup in this day and age, but remember that those stats represent the "decline years" of Howard's career, and are in the form below average right fielder.