The U's now travel to face improving Northampton on Good Friday after their 'worst' display of the campaign and Wilder said: "We can't afford another performance like that between now and the end of the season if we want to achieve."
Morecambe's surprise triumph at the Kassam Stadium leaves Oxford seven points adrift of third-placed Crawley having played a game more.
Northampton will be looking to avenge a 2-0 defeat in the reverse fixture, played just before Christmas when goals from Craddock and Smalley did the damage.