Grimsby prepared for Sunday's FA Trophy final with a lacklustre display as they were beaten 1-0 at Nuneaton.
Boro had scored just two goals in their previous five games but flew out of the traps with Wesley York forcing James McKeown into a save after five minutes.
Kevin Wilkin's men continued to dominate their promotion-chasing opponents and broke the deadlock in the 17th minute when Andy Brown tucked away York's unselfish pull back.
Louis Moult was then twice denied by McKeown before half-time as the Mariners continued to struggle.
Brown had a good opportunity to bag his second of the evening 10 minutes into the second half but he scuffed his shot wide of the post.
Gavin Cowan then headed James Armson's free-kick into the arms of McKeown 12 minutes later as Grimsby showed no threat at the other end, succumbing to their fourth consecutive defeat.