The rest of the first half was quite evenly fought with Grimsby just shading the possession.
The second half saw City up the tempo and get on top from the off. Several moves looked quite promising and it seemed only a matter of time before another was added. The best of these attacks saw Jon Walters cut in from the right side of the box, beat two defenders and unleash a rising thunderbolt of a shot that hit the underside of the bar and bounce away to safety, with 'keeper Paul Fraser well beaten.
As the second half wore on, Grimsby started to come into it a little more, but it was against the run of play when Tony Crane headed home a left wing cross to level the scores.
Either side could have won it, and it went City's way when Clayton Donaldson scored late on to settle the tie at 2-1.
City line-up: Duke; Angus, Hinds, Wiseman, Edge; Price, Fry, Lewis, Donaldson; Walters, Allsopp.