Counter examples don't make it right. Should I list all the players who started off looking promising, had a hiccup and never recovered? There are more of those, btw, they're just less memorable. Started out as a top 5 player at their position for two years, had a hiccup where they were only slightly above average at their position, and the never recovered? At a position like SS? Garry Templeton is the closest example I can think of, and even he was productive for 5-7 years before dropping off. Edgar Renteria had a fairly short period of being near the best at his position as well, but it was never so early on in his career.