To test this hypothesis I implemented this "drop the worst score" grading system for a couple of the rating systems I use for football and measured performance in the usual way. Here are the results for one of the rating systems:
|Predictor||% Correct||MOV Error|
|BGD w/o blowouts or lowouts||72.6%||16.77|
|BGD w/o lowouts||72.9%||16.69|
|BGD w/o blowouts||73.6%||16.62|
Here I'm using the whimsical "lowout" to indicate the worst loss for a team.
As this shows, eliminating the blowouts/lowouts hurts predictive performance. For what it's worth, the losses seem to be more important than the wins. (I saw the same effect in basketball when I looked at this last year.)