Just how much better, if at all, can these four young phenoms get?
There might not be anything baseball fans love more than the promise of improving young players. Just watching a player come up through the system and produce is exciting enough, but it fits in perfectly with the optimistic nature of spring training to know that with more experience in the big leagues, they'll become even more valuable.
There's a ceiling to just how good 99 percent of players are going to be, though, with the other small percentage filling out the ranks of baseball's all-time greats, and the promise of youth isn't enough to separate them: Sometimes players are as good as they'll ever be.
Take Giancarlo Stanton. When the Miami Marlins began to sell off nearly everything of value on the roster, 29 other clubs and their fans jointly salivated over the idea of bringing in a 23-year-old who had just slugged over .600 to lead the majors. The thing is, though, how much better can someone who can do that already get? The next step is to essentially become Barry Bonds, and while that could very well be in the cards, history tells us that it's far more likely that Stanton is maybe as good as he'll ever be already. That, of course, is not a bad thing, when what you are already is Stanton.
We can use projections to give us an idea of the chances players like Stanton have of getting even better. PECOTA, the forecasting system of Baseball Prospectus, doesn't just spit out projected batting lines. It also details the percent chance of a player improving on their expected performances, as well as the chance of a breakout season or a collapse in their production. Using that, we can get an idea of what a long-running projection system thinks of the chances of players like Stanton, as well as other young phenoms like Bryce Harper, Mike Trout, and Jason Heyward have of getting even better.
PECOTA's "Improve" is simple enough to understand. It measures the chance of improving, with the baseline set at 50 percent. Why 50? Think of it as a simple yes or no, with 50 percent going either way, as to whether a given player will improve. So, what we're looking for with this foursome, are Improve scores that shoot well past the 50 percent mark.
As for our young hero Stanton, his improve chance for 2013 came out at 59 percent. PECOTA sees room for growth, but it's not about to hit you over the head with the obviousness of it, instead just giving Stanton a little more potential for it than your typical player. PECOTA mostly sees him replicating his 2012 season, just with a lower batting average, but that's just his most likely projection. Take heart, though, Stanton fans: PECOTA projects him to be the sixth-best hitter in baseball just by being Giancarlo Stanton again, so really, you're just being greedy.
Look to Mike Trout, though, who is two years younger than Stanton, and you get a different story. Trout gets a 69 percent improve rate, but it's not necessarily assuming that 2012 is his baseline, either. Trout's projection for 2013 is "just" .287/.354/.469, a far cry from last season's .326/.399/.564. There are a few obvious items that make this projection understandable: Trout owned a .383 batting average on balls in play last year, and hasn't succeeded in the majors long enough for PECOTA to justify projecting that kind of insanity for him, and his minor-league numbers, at present, suggest he has less power than he showed in 2012.
Now, it could turn out that Trout will post higher than average BABIP -- his career minor-league BABIP is .358 -- and that the aging process helped him out in terms of power. There just hasn't been enough to guarantee that yet, though, so while Trout's upper level projections are likely akin to last year's dominance, his mid-range one is scaled back a bit. The improvement chance is based on what a player has done in their career, though, and Trout has hit .306/.379/.532 over parts of two years, so PECOTA is still giving him plenty of love and a chance at getting even better.
Then there's Jason Heyward, who is right around Stanton in terms of improvement, at just 60. This is a little cloudier than the others, as Heyward has missed time with injury and played through pain, and it's adversely affected his performance. He's hit just .261/.352/.447 in his career after his down 2011 campaign, and PECOTA expects more of the same in 2013. Heyward is a player who might improve more than PECOTA gives him credit for, given his past has been a bit more difficult than Stanton's or Trout's. The meteoric rise of those two make it difficult to realize just how impressive Heyward's three-year run has been, but his OPS+ for ages 20 through 22 ranks 26th all-time, minimum 1,500 plate appearances. He's doing all right for himself.
Last, we've got Harper, who is the youngest of the bunch as well as the most likely to improve. PECOTA pegs him for an 83 percent chance of improving, tops among Major League Baseball regulars, while comparing him at age 20 to the likes of Ken Griffey Jr., Justin Upton, and now, given last year, Mike Trout. PECOTA is projecting a similar campaign to 2012's, with a slightly lower batting average, but part of that is likely just due to Harper's age and lack of experience.
Harper has roughly a season's worth of minor-league numbers to go with his one year in the majors, and while he's been great for his age, he hasn't blown the levels away without that context. That's expected considering he'll just be 20 this year, but it's the primary reason for PECOTA's perceived pessimism. As the player most likely to improve in all of MLB, from a place that many wish they already were, there's plenty of respect here from PECOTA.