A missed penalty from Sam Jones proved costly for Grimsby as they were held to a 0-0 draw by Crawley at Blundell Park.
Jones stepped up from 12 yards after 58 minutes after being fouled by Mark Connolly but he scuffed wide despite sending Glenn Morris the wrong way.
Chances were few and far between in the opening 45 minutes.
Dennon Lewis might have done better with his early opportunity, but he could only drag wide of James McKeown's post after cutting inside from the right.
Crawley defender Joe McNerney then went close with two headers from set-pieces.
While at the other end, a neat one-two between Jones and Scott Vernon allowed the former to prod at goal, only for Glenn Morris to produce a smart stop.
Upon the restart, Jones forced Morris into action once more with a left-footed drive - and then came the telling moment.
Connolly bundled Jones to the ground but after taking on the responsibility himself, the former Leeds man missed from the spot.