There needs to be a catchy two-word phrase, along the lines of “gambler’s fallacy” or “winner’s curse,” for the understandable but generally ill-advised thought pattern that gets applied to guys like Jason Heyward. The rule underlying the fallacy is something like: the more hype a prospect receives upon his debut, the more overlooked and underrated he will become as soon as (inevitably) it turns out that he can’t immediately become Willie Mays or Albert Pujols.

It’s an exceptionally clunkily-worded rule, which is why we need the title phrase.

Heyward’s rookie campaign wasn’t all smooth sailing—he peaked at .301/.421/.596 on May 30, after which, hampered for much of the summer by an injury, he hit just .266/.381/.396—but on the year, he put up a .306 TAv and 4.1 WARP. The WARP was good for 23rd best in the National League, from a guy who played most of the season as a 20-year-old. He’d shown speed, defense, an ability to hit for average and power (both hampered by his mid-summer thumb injury), and an uncanny eye at the plate. He was no Mike Trout, but it was a thrilling debut performance, the kind you can dream a whole Hall of Fame career off of.

Then 2011 happened, and that was bad. That was all it took, really—not that you give up all hope for a young kid after a season like that, but with Harper and Trout coming in and Strasburg coming back, it’s pretty easy to just kind of forget about him.

Then the first two months of 2012 happened, and those weren’t necessarily bad, but they weren’t exactly dream-inspiring, either: on the morning of June 11, Heyward was hitting .245/.329/.440—just slightly above an average line for a 2012 National League hitter, and, as our own Sam Miller noted, strangely similar to the cumulative line created by his great 2010 and horrid 2011 (.255/.362/.427). Sam went on to note:

Jason Heyward this year is very, very similar to Jason Heyward before this year. That’s a bit of a headtrip, because Jason Heyward in 2010 was nothing like Jason Heyward in 2011, and yet the composite they formed ended up resembling, it appears, Jason Heyward’s true self. Heyward was not 2010, or 2011, but somewhere in between. “Somewhere in between” is almost always true, and, because we’re far too easily bored by “somewhere in between,” this is almost always a little disappointing.

That, generally speaking, is right on (it’s Sam, after all, who is never not right on, and who also happens to be editing this piece), and tempering our expectations of guys who are not or barely old enough to drink alcohol legally in the U.S. is never a bad idea.

Only, this time, at the moment the “true self” language above ends up looking a bit premature. In the 49 games in which he’s played since Sam wrote that, here’s what Heyward has done:

.301/.368/.527, 10 HR, 135 (or so) OPS+.

For the year, even after an 0-for-3 with two strikeouts against Cole Hamels on Tuesday, he’s up to .270/.346/.478. His just-slightly-higher line through Monday was good for a 121 OPS+ on the year, within shouting distance of his 131 from 2010. He’s up to a .297 TAv (compare to a .306 in 2010), and 3.8 WARP (vs. 4.1 two seasons ago). In the terms of most of the ways that we measure overall production, Heyward is back to form, and then some. If you believe that the first two-plus months of 2012 are just an extension of what ends up looking like a true “sophomore slump” of 2011, and he’s really turned a corner since mid-June, then he’s even better now than he was in that fantastic 2010.

But then again, one of the things (one of very many, to be fair) that made Heyward such an intriguing prospect in 2010 was his eye at the plate: he walked in nearly 15 percent of his plate appearances that year, a pace that’d get him more than 100 if not for the DL stint. In 2011, his walk rate was down to 11 percent, and in 2012, it’s down even further, to 10 percent. Part of Sam’s point was that Heyward was swinging at a lot more pitches now than he was then, and he still is. What’s more, he’s actually walking just slightly less often from June 11 on than he had been when Sam wrote his piece, and he’s striking out slightly more often (26 percent compared to the prior 24 percent). He’s hitting for a tiny bit more power (while stealing fewer bases), but the single biggest difference is this: when Sam wrote his piece, Heyward’s BABIP was .299; since, it’s been .368 (for what it’s worth, the cumulative .332 is virtually identical to his .335 from 2010).

What does all this mean? I don’t know, but what I think it means is that we don’t really know anything about who Jason Heyward really is. His last two months have been outstanding, but there’s no real reason to pretend that they’re more telling than his first two months, or that either of those sets (or the combined effect of them) is more “him” than his 2010 or 2011 are, either.

This has another implication I’d like to mention briefly: Mike Trout is almost exactly the age that Jason Heyward was two years ago (he turned 21 yesterday). As I write this, he’s hitting .346/.408/.593, with 36 steals in 39 attempts and an oh-my-god-what 19 home runs. This is more than what Heyward did, of course; it’s arguably more than we’ve ever seen a 20-year-old do (Alex Rodriguez and Al Kaline arguably did more, but they had full seasons in which to do it). He’s probably not going to do this every year; he probably won’t do this next year. When, in July 2013, Trout is hitting .285 with six homers and a .340 OBP, it would be really good to remember that he’s 21 years old and we don’t really know anything about him yet. With Heyward, a lot of people seem not quite to have gotten that.

Jason Heyward is going to turn 23 tomorrow. He’s hit .260/.358/.443 in 1517 big-league plate appearances, at an age that (at least as of 2006) falls right between the average ages at Low-A and High-A. He’s done it by being really good for certain lengthy stretches and really bad for others (and average for some more). He could go on being streaky—average to above-average with flashes of brilliance and other flashes of hopelessness—for the next 15 years, or he could just keep getting better and better and become one of the best we’ve ever seen. The most likely result, to paraphrase Sam, is somewhere in between.

The point is that we just don’t know, at all—no more now than we did two months ago or two years ago. But it should be a lot of fun to find out.