He spent the first half of last year (and much of this year) as a 3rd down and goalline back, you're not going to get 1000 yards rushing that way (his first game last season he netted 1 yard rushing and got 3 TDs, when you've got that little room on the field it's hard to stack up the yards). This is the 3rd year when he's been functionally not the feature back (2 years ago the Steelers went to a pass-centric offense so even though he got most of the carries his total number of carries dropped dramatically, he wasn't the feature back last year until Staley got hurt around the halfway point, and when they found out about Parker at the end of last year and in the pre-season this year Parker became the feature back). You're not going to get 1000 yards if you're not a feature back. 7 times this year Bus has been given the ball on 3rd down, 4 of those times he converted; 22 times this year he got the ball on 2nd down, 8 of those times he converted. That's an asset, whether you're willing to admit it or not.
That is all fine but the numbers I'm seeing this year don't keep you in Chicago. Of course the Bears have been more desperate than the Steelers and could not afford the luxury of keeping those numbers at the price.
Anthony Thomas was run out of town with 900 yds his last year here and James Allen was let go after gaining 1000.