Shonn Green's career YPC is 4.2 and was one of the least elusive RBs in the NFL
Ivory has a career YPC of 5.1 and one was of the most elusive RBs in the NFL. Also, it's not the Saints are some amazing running team.. Mark Ingram's YPC is 3.9
Mike Goodson was also on the top end of the elusive rating, but his sample size was too small. (4.5 career YPC)
The fact is, these guys just happened to be burried on really deep RB rosters, and did nothing but produce when they saw the field.
So it appears on paper they are a HUGE upgrade. Shonn Greene can't break tackles, make people miss or catch passes. Other than that we're going to miss him.