In basketball, the transition from college to the NBA is said to be the hardest for point guards.
In football, with the exception of great talents, it's difficult for quarterbacks to come straight into the league and get a taste of success.
In baseball, evaluating talent, especially young talent, is just as, if not more difficult. There will always be exceptional athletes who make grown men plays [insert whatever Mark Jackson joke you'd like here].
Alex Rodriguez and Ken Griffey Jr. are two of the few teenagers that have played like Hall of Famers for most of their careers.
Jason Heyward and Starlin Castro are the most recent youngsters to prove their worth and talent early.
Heyward, 20, hits for power, plays solid defense and runs well. When he figures out the game, there's no indication that he won't also hit for a high average.
Castro, the first player born in the 90's to play in MLB history, has shown glimpses of what the Cubs organization saw when they scouted the young Dominican shortstop.
Today Stephen Strasburg debuts for the Washington Nationals, helping the young franchise sell out a stadium that's usually emptier than the stands at an under 10 roller hockey game.
A lot rides on the arm of the power right-hander, and from how quickly he's disposed of every level of minor league hitter, he might not disappoint.
For young power pitchers, scouts and GM's worry about endurance and longevity.
Scouting young hitters like this year's No. 1 pick, Bryce Harper, is a difficult task.
Most draft picks coming out of high school and various levels of college ball don't hit with wood. They play in smaller fields with aluminum bats that are much more forgiving than the wood, which they'll have to get used to in every level of professional ball.
Against better pitchers, defense and coaching, many young draft picks don't excel as much as they probably should, or as much as the team that drafted them had envisioned.
In baseball, like in so many other sports, the list of players that are great talents but not great professionals, is always expanding.