So here is a look at a few eye-popping, early-season performances, good and bad, and their likelihood of continuing.
Cole Hamels: It has been a rough year for the Phillies, and Hamels' struggles are a significant part of that. He is 1-6 with a 4.61 ERA and leads the National League with 24 walks.
Hamels' velocity is right in line with where it has always been. His pitch assortment is the same as it has been. His line-drive rate is actually down a bit, but hitters are making contact at about the same rate they always have.
The problem for Hamels seems to be something very simple: he is not throwing enough strikes. He has walked 10 percent of the batters he has faced this year, and that is a recipe for scuffling. It is not just walks, either. Hamels is consistently falling behind in the count. He is throwing fewer strikes than ever before. He has seen more at-bats end with him behind in the count than ahead. And when he has been behind, he has gotten tattooed -- hitters are batting .321 and slugging .768 against Hamels when they are ahead in the count.
In short, Hamels needs to throw more strikes earlier in the count, to avoid those dangerous numbers. Given that his stuff is still the same, it seems likely that Hamels will be able to locate his fastball and changeup once again. Odds are, he is going to pitch more like himself as the year goes on.
James Loney: Of all of the surprises, this may be the most surprising. Loney entered Thursday with the American League lead in batting average (.379), a year after hitting .249 and slugging .336 with the Dodgers and Red Sox. He is walking more, striking out less and hitting for more power than he has had in years.
He also has a ludicrous .410 batting average on balls in play, more than 100 points higher than his career average. That is going to come down. Loney has always been a good contact hitter, and he is doing that even better than usual this year, but his high contact rate on pitches outside the strike zone is unlikely to continue.
Loney has shown some encouraging signs. He does seem to have reversed some of the nasty decline that had been plaguing him, and chances are he will be better all year than he was last year. But he is also not going to hit .379 all year.
Shelby Miller: Everyone knows about Matt Harvey. Fewer people seem to know about Miller, which is curious because Miller was always the higher-rated prospect.
They are both young, exciting, hard-throwing right-handers, with two of the best ERAs in the Majors. But they are getting results in totally different ways. Harvey throws four pitches, and he can throw all of them for strikes or for chases out of the zone. Miller is basically a two-pitch pitcher. He has thrown fastballs more than 75 percent of the time. He has thrown either a fastball or a curveball on 98 percent of his pitches.
For a two-pitch starter to dominate Major League hitters on a regular basis is pretty much unheard of. Miller's fastball is very good, and so is his curveball. But if he does not show an ability to use his changeup as well, he is likely to come back to earth some. He has great talent; he will be a good pitcher regardless. But smart money says there is some adjustment needed for Miller before too long.
B.J. Upton: The elder Upton is having perhaps the worst year of any everyday player in baseball. It is far from what the Braves anticipated when they signed him. And distressing is that the peripheral numbers are every bit as dire as the ultimate results.
Upton's line-drive rate has plummeted, and he is hitting more balls on the ground than ever. His contact rate is the lowest it has ever been in his career. He is seeing more strikes than he has in several years, perhaps because pitchers just are not afraid to come in the zone against him.
Upton is not going to hit .145, his average through Thursday, the rest of the year. That seems like a sure thing. But the underlying numbers, behind his baseball-card stats, are genuinely worrying. He will bounce back some, but it will not be shocking if he does not get all the way back to the player he used to be.
Vernon Wells: Wells' contract became a punchline after a couple of unproductive seasons, but it is worth remembering that he was a very good hitter just three years ago. Wells had seasons in 2006, 2008 and 2010 that do not look all that much different from what he is doing in 2013. Yes, he is now 34, and that is a very real difference. But it is not as if he has never demonstrated the ability to hit for average and power.
For one thing, after two years in a very tough place to hit, Wells is now in a friendly ballpark. Even in 2011, he hit for significant power away from Anaheim -- 17 homers in 274 plate appearances. He is making less contact this year, and really the batting average is the one thing that looks like an outlier. But it would not be terribly surprising to see Wells continue his power production all year, possibly even pushing 30 homers.