Quite honestly screen plays were just awful in NFL2k5. I think that has less to do with momentum and more to do with canned animations. "IF" you completed a screen to your halfback the animation was so long and awful you'd almost certainly be crushed by the defense before you even righted yourself to run.
I am thinking more in terms of open field running.....sprinting at an angle toward the sidelines, getting the defensive backs to commit to pursue you at an intersecting angle, then cut back against the flow and watch them try to adjust. As an offensive player you have the advantage of knowing that you are going to cut it back against the grain...so your cut should be almost instantaneous. The defense has to react and should take a bit longer to compensate and try to change their angle of pursuit. This is what that old Madden 2001 did so well in my mind.
It isn't so much the actual controlled runner that I am concerned about. It is the CPU AI controlled defender who can change directions the instant that you do on offense. They need to implement real human like reaction time to achieve this balance again.
The bottom line is the AI reacts and change directions too fast to allow for any real cutbacks in the game. This is in "any" current game I might add.
Peace!