Benson is a guy I think you have to consider drafting on situation alone.
1. In 5 years, Adrian Peterson has 133 carries for the Bears. Granted they drafted Garrett Wolfe, but both of these guys seem more than destined to alternate on 3rd downs, not threaten Benson's workload on 1st & 2nd down.
2. Jones & Benson combined for 453 carries in 2006. If Benson only assumes 75% of that workload, that's still 340 carries.
3. Rex Grossman. I actually think he was unfairly maligned last year but at the end of the day Chicago is going to be a team that is going to put the game in the hands of it's defense more often than not, not it's QB.
So at the very least, assuming Benson stays healthy - he's a lock for a minimum of 300 carries and if he starts to find his groove, could approach 340-350. This is not out of the realm of possibility considering that he never shared the RB1 position in college. If he in fact is a guy who thrives on wearing down the defense as the game drags on (and coming out of college, this is how many forecasted him), then a 4.3-4.4 YPC is plausible as well.
So top end rushing forecasts for him could look like this:
345 carries at 4.35 YPC = 1500 yards.
I think the interesting thing about Benson is how universally disliked he appears to be. Simply put though, he is vital to the Bears success and I see him as developing into a Rudi Johnson clone who does not have the aerial attack Johnson does to compete with. In addition, he will be the goal line battering ram. As such, I see Benson as being a much lower risk than perceived investment and trend towards him hitting the high end of the expectation curve.
Prediction: 334 carries, 1436 rushing yards, 13 TD's; 21 receptions 142 receiving yards, 0 TD's.