Leicester fielded as good a side as they could within the constraints of a heavy injury list, wary as they were of the team that defeated Sheffield Wednesday in the second round. The reality was that, after leading from the 16th minute until the 68th, Leicester collapsed under incessant pressure.
A pretty sight it was not, but mightily effective. Leicester, having looked comfortable, crashed to earth by conceding three goals in little more than 10 minutes. For their pains, Leicester had Julian Watts (concussion) and Steve Walsh (suspected broken arm) taken to hospital in consequence of the home side's freakish second goal.
Ian Marshall delivered a swift pay-off as Leicester achieved the early superiority, diving in at the far post to head home Robbie Savage's cross.
Moments earlier, the defender Graham Rodger had denied Marshall as the striker took aim from 15 yards but soon Leicester found themselves forced into retreat as the home side sought a quick reply, a series of corners requiring Kasey Keller, their goalkeeper, to be on his mettle.
He was not tested enough, however, teenager Danny Butterfield - released by Leicester two years ago - shooting wide and Kingsley Black thundering a 20-yard free kick into a wall of blue. But then Steve Guppy missed a chance to duplicate Marshall's goal when Savage delivered another telling cross.
At half-time, however, Grimsby replaced Black with Steve Livingstone and switched to 4-2-4, taking Leicester by surprise to the extent they could scarcely escape their own half.
Keller made some brave saves but Leicester were allowed no respite and when the first-half substitute Kevin Jobling drove home an equaliser inside a crowded penalty area it was no more than Grimsby deserved.
Not content, however, they went ahead four minutes later, Livingstone's header rolling into an ungarded net after Keller and Watts collided. Watts was carried off on a stretcher. Walsh, who ran into a post trying to stop the ball, left the field shortly afterwards.
Leicester were groggy now and Livingstone pounced again to turn in Peter Handyside's deflected shot.
Grimsby Town (4-4-2): Davison; Butterfield (Jobling, 35), Handyside, Rodger, Gallimore; Donovan, Groves, Widdrington, Black (Livingstone, h- t); Lester, Nogan. Substitute not used: Woods.
Leicester City (3-5-2): Keller; Watts (Wilson, 76), Elliott, Walsh (McMahon, 79); Savage, Campbell, Lennon, Fenton, Guppy; Marshall, Cottee. Substitute not used: Arphexad.
Referee: M Riley (Leeds).Reuse content