A late first half penalty from former Cheltenham Town forward Wes Thomas saw Cheltenham slip to defeat on the road at Grimsby.
Thomas stroked in from the spot to see the Robins suffer a second consecutive away defeat.
Following last week's defeat at Colchester, Conor Thomas, Jacob Maddox and Cameron Pring were brought into the starting XI as Michael Duff aimed to shuffle his pack.
But they couldn't prevent a consecutive away loss in a game of limited chances.
Early on it was the hosts who had the better openings. Thomas prodded wide after good build up play on the left and Scott Flinders made a comfortable stop to deny Martyn Woolford.
Steadily Cheltenham came into the contest. Luke Varney steered a lively Chris Hussey free kick wide, while Rakish Bingham's shot was blocked after he met Varney's pull-back.
Varney had the ball in the back of the net only for it to be ruled out for an obvious offside following Kevin Dawson's through ball, but the ball was in the net again at the other end when Grimsby took the lead minutes later.
Thomas was brought down in the box and he stepped up to fire in his tenth League Two goal of the season to break the deadlock.
The second half proved to be very much a no show with very little between the two teams. A flood of substitutions from both benches looked to provide the spark to liven the contest up, and Robins fans would have been pleased to see Will Boyle return from injury.
Finally on 80 minutes there was the first opening of the half. It fell into the path of Grimsby substitute Kristian Dennis who saw his strike saved by Flinders.
The Robins had struggled to create opportunities to find a way back into the tie, but they got one on 82 minutes when Jacob Maddox was upended, only for Hussey's whipped free kick to go past the post.
It was all that they could truly muster towards the finish, as despite a stoppage time corner kick which saw Flinders join the attack and come to nothing, the Mariners held on to gain revenge for their late defeat at the Jonny-Rocks Stadium earlier in the season.
GRIMSBY: McKeown, Hall-Johnson, Ring, Ohman, Collins, Hessenthaler, Cook, Woolford (Clifton 64), Embleton (Davis 83), Hendrie, Thomas (Dennis 74)
Subs not used: Russell, Grayson, Vernam, Whitmore
ROBINS: Flinders, Hussey, Tozer, Thomas, Dawson, Maddox, Raglan, Tillson, Bingham (Waters 56), Pring (Boyle 72), Varney (Duku 65)
Subs not used: Lovett, Broom, Forster, Clements
ATTENDANCE: 4940 (82 Robins)
REFEREE: T Kettle