Parker's the #1 rusher in the league, a pro-bowl bound undrafted star that is explosive on offense... As much as I sometimes dislike his style because of his size issues, Davenport is no Parker... Not to say Davenport can't hold his own, but Davenport tends to run more like Bettis than Parker, and the factors that he'd need to succeed are not real good..
He looked good against the rams, but he bounced most of his runs to the outside that he had large gains on. Doing that against a team with a strong defensive line, or even strong defensive ends, is going to be difficult for him... Parker could exploit defensive ends even if they were all-stars... Davenport isn't going to be as successful.
As a Steelers fan, I am hopeful, but as a realistic person I'm looking at it cringing... Not to mention our offensive line's pass blocking isn't their only problem they have at times. Against strong defensive teams, we may not be able to open holes for Davenport to get little (or big) runs up the middle, and you can't bounce every run to the outside.
It was a huge, HUGE loss for them... Davenport's not bad or he wouldn't be there, but he just isn't capable of the things Parker does I'm afraid.