A STUNNING, match-winning full debut from Tom Naylor provided the Mariners with perhaps the best result of their campaign so far.
The on-loan defender stepped in for the injured Shaun Pearson, kept a clean sheet and scored the only goal of the game on a fantastic evening for Town and their fans last night.
After the postponement of Friday evening's scheduled encounter at Macclesfield Town, the Mariners made it to The New Lawn in plenty of time for kick-off.
With Pearson ruled out with a knee problem, Naylor stepped in at centre-back. Elsewhere, Aswad Thomas returned at left-back, but not at the expense of Bradley Wood as expected – instead, Sam Hatton made way as Wood switched sides.
Richard Brodie also returned to the starting XI to partner Andy Cook, as Ross Hannah had to make do with a place on the bench. Jamie Devitt joined him among the substitutes, with Joe Colbeck and Marcus Marshall the starting wingers.
For the hosts, former Town loanee Ben Wright was another substitute, while Al Bangura – a Premier League player with Watford just six years ago – began in the centre of a three-man midfield.
The game was into its 12th minute before there was anything to raise the pulse – Lee Fowler slicing a speculative 30-yard effort well wide of James McKeown's goal.
A minute later, Thomas set off on his first rampaging run of the evening before his cross was clumsily pushed around the near post by keeper Sam Russell.
The corner came to nothing, but the match had started for real.
Bangura saw a low drive blocked by Naylor seconds later, before Marshall broke at pace and earned a free-kick right on the edge of the Rovers box, which Brodie smashed into the wall.
The combative forward then earned another booking to add to his list, for a needless pull-back.
Yan Klukowski swept a Forest Green free-kick just over McKeown's bar in the 22nd minute, and five minutes later Magno Vieira smashed another attempt high and wide.
In the build-up to that effort, Derek Niven had collapsed in a heap near halfway, and the central-midfielder was immediately replaced by Andi Thanoj with a 'worrying-looking' injury.
Fowler volleyed over from 30 yards – again – shortly after the half hour mark but, despite the Town change, the game remained a cagey affair.
As usual, the Mariners were looking solid, organised and resolute, but – not for the first time this season – their forwards were isolated.
The first shot on target of the clash arrived in the 41st minute when James Norwood got the better of Wood before testing McKeown with a low drive from just inside the box. Needless to say, the Town keeper was more than equal to it.
But he had a real scare in the last minute of the half as Chris Stokes found his way through the visiting defence and guided his shot past the stopper, but onto the foot of his far post.
It was a let-off for the Mariners, and after McKeown had held onto Klukowski's powerful free-kick, that was the end of the first half action.
Town had early shouts for a penalty after the break when Marshall thought he had been blocked off, but referee Peter Bankes couldn't have looked less interested.
GALLERY: Forest Green Rovers v Grimsby Town
Forest Green reacted by forcing a couple of corners in quick succession, the second of which Fowler ballooned over the bar from distance again.
The visiting Mariners finally had their first shot of the night in the 58th minute as Marshall fed Thomas on the overlap and the full-back's stinging drive needed pushing away by Russell.
Within moments, a much-improved Town were on the attack again – from Colbeck's free-kick – as Craig Disley won the header, Brodie touched the ball off, and Ian Miller sliced his first-time effort wide.
Cook's deflected drive, on 63 minutes, was easy for Russell, before his strike partner, Brodie, made way for Lenell John-Lewis.
Disley then hammered a 25-yarder wide as the game continued to open up, and Colbeck got around his marker before seeing his pull-back smashed clear by the Forest Green defence with Marshall waiting to pounce.
Town were on top and earned their reward 15 minutes from time.
Cook did superbly on the left to win the ball for Thanoj to drill a cross in, and Naylor was the man on the spot as Russell dropped the ball under pressure, to flick home from five yards out.
It was no more than the Mariners deserved for their second half display, if not their first.
And, although the hosts huffed and puffed to force their way back into the game, Town were in no mood to relinquish such a precious advantage.
In fact, Rovers couldn't muster another shot on goal over the remaining 16 minutes – plus three extra ones – as Hatton replaced Thomas for the closing stages.
And at the final whistle the 199 Mariners fans who had made the long journey to the south west celebrated as if the title was already won.
There are sure to be a few twists and turns yet, but it was a potentially huge result in Town's quest to return to the Football League.
Replay our live and interactive coverage below: