There had been some speculation about this, but looking at this logically, it didn't really make a lot of sense. Jamison had a good season, and is an improving player, but he had trouble staying healthy this year, and could have definitely improved his stock with a good 2013. Some would argue that this year's crop of RBs is going to be weak, but I still don't really see Jamison being a high pick. If he came back and had a strong 2013, his stock would have probably risen to the third round range. Perhaps Jamison sees his stock rising during the pre-draft workout process, or is worried about the well-documented short shelf live for running backs in the pros.
Rutgers should be fine with former blue chipper Savon Huggins starting, who did look good in his limited opportunities this season. The problem is more behind him, where the team has walk-on Paul James, speedster Ben Martin, and spark plug Des Peoples, none of whom have seen especially a lot of in game action. That doesn't mean that they can't play, but this definitely will open up the competition in April. Dontae Ayres is signed for this year's class, and there's always the possibility that Rutgers could try to get back into the mix with some other RB prospects as well.
Sure, this is a loss. Jawan Jamison is a good player, and although I think Huggins probably has more raw talent, Jamison's slashing running style was a better fit for Kyle Flood's offense than Huggins, who is more of a straight-ahead type. It's not devastating though. It'll be tough, but Huggins can fill Jamison's shoes. Losing a potential first round pick in Logan Ryan, at a spot where Rutgers is hurting for depth looms as a far bigger loss.