I think that Streveler's performance, miscues and all were the result of him trying to gamble and win the game that was slipping away. He did not look good, but he may yet be salvageable, as Vernon Adams was in Montreal.
You are assuming that it would be better if Nichols was not injured. The deficiencies in the team were becoming evident even before he went down. And the coaching has remained the same.
I think hanging all this on Streveler is a gross over-simplification. We still do not have have receivers who will go fight for the lobbed balls or the coordinators who can adjust game plans on the fly.
O'Shea has chosen, supervised, assessed and defended his coordinators. His judgement is suspect at the very least and does not inspire confidence in him as a head coach.