This study covered 2008 through 2009 and it showed some interesting things. It basically said returning starters are a bit over-rated. There is a minimum threshold though. If you don't have enough overall experience returning your team will get killed. It showed that a returning RB really didn't matter but QBs and WRs did. Interesting read.

http://mgoblog.com/diaries/how-valua...-most-valuable