With over a month remaining in the regular season, Mike Trout’s campaign already looks like it might be remembered as the best ever recorded by a rookie. But Trout’s 2012 may have another lasting legacy: spoiling future rookie seasons for the rest of us. While watching Trout run roughshod over opposing AL pitchers, it’s easy to forget how rare it is for first-year players to be stars, let alone leading MVP candidates. However, it takes time for most young players (including Trout himself last season) to find their footing: only one other rookie, 26-year-old Yoenis Cespedes, has amassed even a third of the value of the Angels’ outfielder this year.
Even highly rated rookies usually struggle in their initial exposure to big-league pitching, and those who find success at first often suffer in their second trips around the league or in their sophomore seasons, as opponents start to exploit their weaknesses. Some of them recover quickly from these setbacks. Others take years to adjust, and many never put together the production that was expected of them.
The following 10 players ranked among the best 100 prospects in baseball at some point in the past decade, but they’ve all taken their lumps in the big leagues. This season, though, they look like they’re back on track to fulfill their potential. But are they here to stay, or are they deceiving us again?
Chris Carter, Athletics
No one ever questioned Carter’s patience or power. They questioned whether he could hit breaking balls. The answer to the second question still seems to be “no,” but that hasn’t slowed the A’s big first baseman. The 25-year-old Carter entered this season with a .167/.226/.254 career line and just three home runs amassed over 124 plate appearances from 2010-11, but he’s cranked home runs at the fifth-highest rate in the AL in 2012. The problem: only one of his 12 homers came against a breaking ball. Carter is crushing fastballs, batting almost .350 and slugging close to .800 against them, but he’s hit .133 and slugged .244 vs. curveballs and sliders. If those splits persist, it’s unlikely that opposing pitchers will continue to feed him fastballs at an above-average rate, and more breaking balls would be bad news. Carter isn’t out of the woods yet.
Pedro Alvarez, Pirates
Perhaps made complacent by a solid rookie year in 2010, Pedro Alvarez let his conditioning slip and suffered from an injury-filled and ineffective sophomore season. Several weeks in Indianapolis failed to straighten him out, and he hit just .171 for Pittsburgh in September. His third big-league season didn’t start much better: through June 15th, Alvarez hit .189/.254/.373. Since then, though, he’s been one of the best hitters in baseball. Alvarez’s .328 TAv after June 15th ranks eighth among hitters with at least 200 PA (but only third on the Pirates, thanks to Andrew McCutchen and Garrett Jones), and fortunately for St. Louis, much of his damage has been done against a division rival. His 26 homers tie him for the fourth-highest total in the NL. The power that made Alvarez the second overall pick in the 2008 draft is the same power that’s propelling the Pirates now. There’s still too much swing-and-miss in his game, but it should be smoother sailing from here.
Brett Wallace, Astros
The knock against Wallace in recent years has been that his bat is a little too light for first base. He entered 2012 with a career .248/.323/.354 line, which is a little light for shortstop. So far this season, he’s hitting .298/.367/.500, which is plenty of offense for any position, but that’s not likely to last. Wallace is a liability against lefties, and his success against righties is built on a fluky BABIP. His batting average is unsustainably high for someone who strikes out as often as he does—among hitters with a strikeout rate of at least 29 percent, Wallace has the highest average by almost 40 points—and he’s done most of his damage against fastballs. He makes little contact outside of the zone, so like Carter, Wallace could tank if he starts seeing more slow stuff.
Dexter Fowler, Rockies
This is Fowler’s fifth big-league season, but it will be his first without a trip to Triple-A. In each of the last two seasons, a slow start was followed by a stint in Colorado Springs, which was in turn followed by a second-half hot streak. This time, he’s sustained that hot streak into the next season: his .288/.381/.498 line from the second half of 2011 presaged his .306/.392/.496 line in 2012. Fowler’s 12 homers are a career-high at any level, he’s leading the league in triples for the second season, and he even seems to have figured out southpaws. His improved power is largely a product of Coors Field, but as long as his plays half his games there, he’ll live up to his prospect pedigree.
Todd Frazier, Reds
Frazier’s greatest problem has been a lack of opportunity, not paltry production. With Joey Votto, Brandon Phillips, and Scott Rolen arrayed around the Reds’ infield, Frazier didn’t get his first crack at the majors until last season, at age 25. He showed good power in 121 PA, but a low BABIP sapped his slash line. With both Rolen and Votto doing time on the DL this season, Frazier has seen more action at the infield corners, and he’s made the most of it. His 2.3 WARP leads all rookie NL hitters, and Votto is the only Cincinnati player with a better batting line. With Rolen hitting well, Jay Bruce and Ryan Ludwick entrenched in the outfield corners, and Votto close to returning, Frazier is about to see his playing time curtailed again. “Sometimes when you’re on a really good team, you’ve got to wait your turn to play,” Dusty Baker explained, but Frazier learned that lesson long ago. Rolen is a free agent after this season, so Frazier’s wait for a starting job will almost certainly end in 2013.
Edwin Encarnacion, Blue Jays
Encarnacion remains a liability in the field, but he can’t do much damage splitting time between first base and DH. He’s saved most of the damage for the batter’s box. Encarnacion has been an above-average hitter since his second season, but “above average” doesn’t begin to describe his breakout 2012. Among AL batters with at least 400 plate appearances, only Mike Trout can top Encarnacion’s .332 TAv. Before the 2005 season, Baseball America ranked Encarnacion the 56th-best prospect, praising his “willingness to go the other way,” but noted that “his swing tends to get long when he tries too hard to hit for power.” This season, Encarnacion shortened his swing, and as a result, those balls he hits the other way and up the middle are going much farther. It took time for him to make the most of his talent, but Encarnacion became even better than Baseball America thought.
Carlos Gomez, Brewers
It’s been well over four years since Gomez was sent to the Twins in the Johan Santana trade, and he’s long since moved on from Minnesota, but we’re starting to see why his inclusion got that deal done. Shortly after the trade, Kevin Goldstein praised Gomez’s “gap power” but noted that he needed to “make significant changes in his approach in order to take advantage of his raw skills.” He didn’t do that until last season, when he started to elevate, driving the ball in the air rather than slapping it on the ground and attempting to beat out base hits. At 26, he has impressive power for a player with the speed to play a strong center field and excel on the bases. He’s still too impatient to be an impact player, but in other respects, he’s much more refined. It’s a pity the Twins won’t reap the reward.
James McDonald, Pirates
McDonald missed much of spring training in 2011 while suffering from left trunk soreness, but he rushed back to make the Opening Day roster anyway. That may have been a mistake. Take away McDonald’s five ugly April starts, and he would have finished with a 3.63 ERA. His ERA this season? 3.57. McDonald has relied more heavily on a slider in 2012, but his success is an extension of what we saw last season. Three years ago, before he was traded to Pittsburgh in one of the many deadline deals involving Octavio Dotel, McDonald was a promising prospect for the Dodgers. Now we know why.
Jeff Samardzija, Cubs
Before this season, Samardzija looked like he’d never be worth the big bonus the Cubs gave him to commit to baseball. The Cubbies converted him to the bullpen in 2011 to salvage some value, and while he showed an improved ability to miss bats, he was as wild as ever. This spring, Samardzija was moved back to the rotation, and he’s finally found the strike zone. Actually, it might be more accurate to say that he’s found strikes, since many of them have been outside of the zone: Samardzija retained the velocity he gained in the bullpen even after returning to the rotation, and the combination of a nasty splitter and one of the hardest heaters in the game has led to many more chases and whiffs. It took too long for the Cubs’ comfort, but Samardzija has become a dependable arm.
Rick Porcello, Tigers
Porcello’s 4.60 ERA isn’t pretty, and he leads the AL in hits allowed, but that’s largely a product of the Tigers’ porous infield. FIP is a truer gauge of Porcello’s talent, and his 3.60 mark is 11th-best among qualified AL pitchers. Porcello’s improvements have been incremental but constant, and his strikeout, walk, groundball, and home run rates are all career bests. On another team, or with better defenders behind him, his maturation would be more obvious.
Honorable mention: Josh Reddick, Athletics; Jason Hammel, Orioles; Tyler Colvin, Rockies; Alcides Escobar, Royals
​A version of this story originally appeared on ESPN Insider 
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Also, on an unrelated note, where are today's Playoff Odds?
We're working on getting the odds up--there was a delay in our nightly update process.
I would love to see a list of prospects that were football oriented in HS and see if they are a year or 2 behind other prospects drafted.
This leads me to my next question: much like the football theory, are there any things we can look for to predict the next crop of "late bloomers"? A great follow up to this would be a list of guys who have lost some of their prospect shine but may be candidates to make a list like this next year.