It's important to understand how a player ends up being in the top 20 in the league in scoring. Let's look at his performance in the seasons before and after that performance:
This list goes back to 1996-97, which gives us nine sets of consecutive seasons (ie - 2003-04, 2004-05, 2005-06 and 2009-10 do not have a full season before and after them.) Overall, 75% of players who finished in the top 20 improved their scoring totals from year -1 to year 0 (the year they finished in the top 20). Then 79% of those players regressed from year 0 to year 1. Essentially, in year 1, they went back to what they were before, which means a 10% drop in their scoring rate, and a 10% drop in games played. If we knew nothing else about a player, except that he finished in the top 20 in scoring, we should expect him to do significantly worse in his next season.
Long story short: if you want to be right, bet the under.