Evaluating baseball prospects sometimes seems like a preposterous idea: Take a teenage kid, project him four or five years into the future and predict whether he'll develop the ability to hit breaking balls or whether he'll add velocity to his fastball (or lose velocity). Then factor in all the intangibles: Will he deal with failure? Will he stay healthy? Does he have that desire to get better and work at his game?
It's remarkable that the evaluators do as well as they do. Sometimes they're right in predicting a guy as a future big leaguer, but underestimate on his ultimate upside. Here are a few stars who turned out better than expected.
Peak prospect rating: Never a top-100 prospect
Quote: "Altuve fits no standard profile. He doesn't lack tools, but he's difficult to compare to other players. ... He may put up big numbers at Lancaster this season but will have to keep proving himself at higher levels to scouts who remain skeptical of a player with such a small body." -- 2011 Baseball America Prospect Handbook
With Altuve, it was all about his lack of size and the inability to look past that. As noted, his skills were always there, everything you'd want from a second baseman: The hit tool, speed, defense, even a little pop. He produced in the minors at a young age as well, which should have been more evidence that he had a chance to be a special player. Yet Baseball America ranked him as Houston's 28th-best prospect entering 2011. Kevin Goldstein of Baseball Prospectus -- he now works for the Astros -- was a little more optimistic, ranking Altuve 11th in Houston's system, writing, "Altuve is so unique that it's hard to figure out just what he can be. At the same time, it's hard to argue with his talent."
Peak prospect rating: No. 42 Baseball America, No. 20 Baseball Prospectus
Quote: "Lacks prototypical profile for third base; swing shows linear plane; stays in zone a long time, but not designed to lift balls; struggled against RHP; weak contact and problems with vertical movement; well below-average speed; range at third is merely adequate." -- Baseball Prospectus, Rockies top 10 prospects 2013
That quote came after a Double-A season in which Arenado had hit .285 with just 12 home runs in 135 games, seeing his prospect luster drop from the previous season, when he'd had a strong year at Class A. He fell from No. 20 to No. 57 in the Baseball Prospectus rankings and to No. 52 in Baseball America. Everyone loved Mike Olt that offseason. If there's a lesson there, it's contact ability, especially when comparing Arenado to Olt. Arenado always had it and it's easier to make adjustments to your game if you have that natural hand-eye coordination. He obviously has learned to add loft to the game, turning him into a 40-homer guy, but the interesting thing to me is his defense. When in the minors, the Rockies at one time considered moving him to first base. It's hard to believe a guy this good once looked that bad. Baseball America liked his defense before the 2013 season, giving it a 60 rating on the 20-80 scale, but I don't think anyone saw him as a perennial Gold Glove winner.
Peak prospect rating: No. 39 Baseball America, No. 60 Baseball Prospectus, No. 57 Keith Law
Quote: "Nola's hallmark is his stellar command, which stems from good athletic ability and freakish flexibility. His fastball checks in at 93-95 mph and gets excellent life from a mid-three-quarters arm slot. He backs up the fastball with a slider and changeup, which each have the potential to be plus in the future." -- 2015 Baseball America Prospect Handbook
Nola was the seventh overall pick in the 2014 draft out of LSU, so it's not as if he has come out of nowhere. But he was described as a guy with a higher floor than ceiling -- a good bet to make the majors but more likely to settle in as No. 3 starter than an ace. It always seemed a little odd that the Phillies would take a pitcher without major upside that high in the draft. Well, maybe the Phillies knew something because Nola is currently pitching like an ace: 3.13 ERA, 46 IP, 31 H, 8 BB, 49 SO, 3 HR. His knockout pitch is a curveball that might be the best in the game right now. What's interesting is that his pitch was always described as a slider, not a curve. Whatever it is, it has been almost impossible to hit: Batters are hitting just .074 against it (they hit .191 last year). Note as well from that piece I linked to that Nola has moved from the middle of the rubber to the first-base side.
Nola's average fastball velocity is actually just 90.0 mph, so less than than the ranges described as an amateur. But note what Keith Law wrote last year: "Nola has grade-70 command of his 91-94 mph fastball, with very good life on the pitch, locating it where he wants to either side of the plate and showing little fear when working with it." It's the big velocity that gets pitcher a high ranking on the prospect lists, but if you have grade-70 command and movement, that's a road to success as well.
Peak prospect rating: No. 47 Baseball America, No. 69 Baseball Prospectus
Quote: "Despite his numbers, there are some major weaknesses in Rizzo's game. His power nearly disappears against left-handers, and he has a hitch in his swing that often leaves him behind good velocity. Despite his natural strength, he has a tendency to get pull-happy and hunts for power, which led to some silly swings against breaking balls in the big leagues." -- Baseball Prospectus top 10 Padres prospects 2011
Rizzo was traded twice as a young player, first from the Red Sox to the Padres as a minor leaguer, and then from the Padres to the Cubs after he hit .141 in 49 games with the Padres in 2011 in his first big league trial. Given the scouting report above, it probably wasn't a surprise Rizzo struggled initially, with the Padres giving up on him too quickly (he was traded for Andrew Cashner). Prospect rankings are always cautious with first basemen because everything rides on the bat, but if there's a lesson with Rizzo's development, it's his age. He was very young for his leagues, getting drafted out of high school when he was still 17 and playing in Double-A at age 20. Certainly he has made adjustments, but the fact that he had 25 home runs and 42 doubles while drawing walks at age 20 was a good sign that his bat had All-Star potential ... this year, MVP potential.