86.8% of the 2010 rookies returned to play again in 2011. (37 of 281 did not return)
You need to compare that to the 2011 overall return rate of 91.5% (91.2% if you discount the rookies who did return) to make a valid comparison next year.
There are some historical numbers
here for how long teams last after their rookie year.
A description of the numbers is given
here by the author.