Stanford pitcher Mark Appel was the top overall selection, by the Houston Astros, in this year’s draft. (AP Photo/Eric Risberg)

Ten years ago, the Chicago Cubs used the sixth pick in Major League Baseball’s draft on a power-hitting right fielder from Dunedin (Fla.) High, Ryan Harvey. The papers the next day took the obvious storyline, that the woebegone franchise had found its heir to slugging right fielder Sammy Sosa.

“He has great talent,” then-Cubs scouting director John Stockstill said then. “He just needs to translate it to power at the big-league level.”

Harvey is now 28, and he has hit 117 home runs in the minor leagues. But he never translated that power to the big-league level, and he is now in the midst of his second season with Lancaster (Pa.) Barnstormers of the independent Atlantic League.

With the MLB draft conducted this week, Harvey’s story is pertinent as scouting directors and general managers around the league boast about their haul. “I know what I’m going to say before the draft,” one scouting director said two days before the first pick. “Same every year. ‘We never expected this guy to be here when we picked.’”

As much as scouting gurus in baseball work countless hours and rack up enough frequent flier miles to transport the starting nine for a full year, they can’t take all the guesswork out of projecting how an 18-year-old’s skills might develop. In the 2003 draft that produced Harvey, the first round featured five players who went on to make all-star teams, but only one who did so more than once (outfielder Carlos Quentin). But seven players — including Harvey and two players drafted ahead of him — outfielder Chris Lubanski and pitcher Kyle Sleeth — never made the majors.

So while the Houston Astros are excited about top overall selection right-hander Mark Appel from Stanford, they also know that just two of the seven top overall selections between 2002-08 have become all-stars. The top 10 selections in those drafts have produced 13 all-stars and eight players who have yet to reach the majors. (And that includes the incredible 2005 draft, in which five of the top seven players chosen — Justin Upton, Ryan Zimmerman, Ryan Braun, Ricky Romero and Troy Tulowitzki — have appeared in at least one all-star game, and none of the top 10 picks failed to make the majors.) (Oh, and throw in picks 11 and 12 in that draft – Andrew McCutchen and Jay Bruce – and it’s seven of the top 12 as all-stars.)

So even with all the excitement surrounding each one of those high picks, the best course — for fans and execs — is caution.