Vale lined up with their unusual 3-2-2-3 formation which was always likely to cause problems in the gap between midfield and defence. One time Mariners target Marc Bridge-Wilkinson started in the Valiants midfield whilst the highly rated Stephen McPhee partnered veteran Adrian Littlejohn up front.
Vale started the brighter with both McPhee and Brooker testing Aidan Davison from long range.
Vale's best chance of the first half came when slack defending saw Littlejohn unmarked but the former Sheffield United man was unable to beat the impressive Davison in a one-on-one situation.
Davison continued his impressive performance throughout the game and his commanding presenece was a welcome sight.
Town took a possibly undeserving lead on 39 minutes. Marcel Cas bombed forward from right-back to provide a delightful cross for the rising Michael Boulding who headed beyond Dean Delaney's dive for his second goal of the season.
With Town possibly looking their most comfertable of the game, the self destruct button was pressed once again. Iain Anderson led with his arm into an aerial challange with Michael Walsh and was show the red card by referee Phil Prosser.
Groves replaced the, once again, disappointing Ten Heuvel at half time as Town went 4-4-1 to try and defend their lead.
Early in the second half Boulding should have made it safe but Delaney snuffed out his weak shot after been played through by Campbell's intellegent ball.
The former Mansfield pace man was soon replaced by Darren Mansaram after spending the best part of 60 mintues chasing hopeless long balls to no avail.
Despite the one, two if you want to include Mr Prosser, man disadvantage Town looked in control. Until minute 65 that is. Darren Barnard messed up a easy header allowing former Coventry hitman McPhee to sneak in, round Davison and finish to pull Vale level.
3 minutes later and Town were behind. Ryan Brown crossed from a free kick on the right side only for every Town player to stand ball watching whilst sub Billy Paynter strolled in and finished past the helpless Davison.
Jason Crowe was sacrificed by Groves in favour of Jonny Rowan as Town returned to two up front but glorious chances missed by Mansaram and captain for the day Stuart Campbell prevented any chance of a comeback.
A late appeal for a penalty was turned down by Prosser despite the Vale defender clearly handling the ball.
Poor refereeing aside, Town are in danger of losing sight of the early leaders and performances and tactics like this will see Groves' men fail to return to the 1st division at the first attempt.
Grimsby: Davison, Cas, Ford, Crane, Barnard, Crowe, Campbell, Hamilton, Anderson, Boulding, Ten Heuvel. Subs: Mansaram, Groves, Rowan, Edwards, Pettinger.
Port Vale: Delaney, Pilkington, Walsh, Collins, Cummins, Lipa, Bridge-Wilkinson, Brown, McPhee, Brooker, Littlejohn. Subs: Rowland, Armstrong, Paynter, Boyd, Molloy.