A first-half double from full debutant James Roberts put the hosts in charge and when Danny Rose hammered home the third, the tie was all but over as a contest – a late consolation from Mariners’ defender Shaun Pearson not being enough to spark a dramatic comeback.
The two sides came into the game with contrasting fortunes; the U’s struggling at the foot of League Two, whilst the Mariners had won their last five in all competitions to go second in the Vanarama Conference.
And the respect that former Mariner Michael Appleton had for his former side was evident as his side lined up to mirror the team that had sent Grimsby to those five victories, with defender Andrew Whing taking up a berth in front of the back four to try and stifle any home attacks.
But for home boss Paul Hurst there was some reshuffling to be done and his side had more of an attacking edge to the starting XI than in recent weeks.
Injury to Carl Magnay and loan midfielder Harry Pell’s ineligibility meant returns to the side for another loan man Danny Parslow, returning from York, and striker Jon-Paul Pittman.
Despite an impressive start from the hosts, they struggled to come to terms with their own system in the opening 45 minutes, flitting between a regular 4-4-2, a 4-4-1-1 with Nathan Arnold sitting in the hole and a 4-2-3-1 with Arnold, Pittman and Jack Mackreth all in advanced positions – whatever they reverted to seemed to be unfamiliar territory for the side.
The adrenaline was flowing at Blundell Park in the opening 15 minutes though and the Mariners were unlucky not to take the lead with the game’s first real opening.
John-Lewis controlled a ball around 30 yards from goal and turned past his marker before gliding past two more challenges. His low drive was powerful and beat visiting stopper Ryan Clarke but cannoned back off the upright and to safety.
Mackreth had been asked to take up a role on the left-hand side of the Town side and he caught the eye in the early exchanges with a weaving run across the box, before Clarke turned a low shot away for a corner.
From that 19th-minute set piece the away side took the ascendency. The ball was cleared long, looking for the run of the U’s Alfie Potter. Mackreth did superbly to get back and cover but his back pass to James McKeown was weak and forced the ‘keeper out to make a fine block, preventing the Oxford man from opening the scoring.
McKeown was called into action again seven minutes later as he tipped over an inswinging Brian Howard free kick that had caught on the wind and looked destined for the top corner.
But Appleton’s men could sense an opening and it duly followed on 33 minutes. Again it came from a wayward Mariners’ set piece, as the U’s broke at pace with Roberts cutting in from the left and firing in a curling right-foot shot that McKeown could only fingertip into the corner of the goal.
The lead should have been doubled within two minutes. Joe Riley chased down a lost cause and kept the ball in play. His cross eventually found Howard but the former Barnsley man didn’t get enough purchase on his half volley and that allowed Craig Disley to clear off the line for the Mariners.
A second U’s goal did arrive four minutes before the break and it was Roberts who was on hand again to claim it. Craig Clay gave the ball away in midfield with a lax header and that allowed Potter to sprint down the left unchallenged.
His cross was palmed away by McKeown, straight into the path of Roberts, who made no mistake from six yards. It was now an uphill task for the home side and they only had a wild effort from defender Aswad Thomas to show for their efforts in the closing moments of the half.
Manager Hurst reverted to an orthodox 4-4-2 in the second half; Mackreth coming out to his more familiar right-wing slot, with Arnold taking up the place on the opposite flank, as Pittman joined John-Lewis up top.
But it was to get worse for the hosts within five minutes of the restart. Again Potter was the provider, getting to the byline and pulling the ball back for Rose to thunder home a shot from 12 yards.
Town did respond well and pressed in vain to get a foothold back in the game. The side’s main consternation was reserved for the match officials, who turned down clear-cut penalty appeals for John-Lewis and Pittman.
A glimmer of hope arrived with 12 minutes left on the clock. Parslow kept a set piece moving and his header was latched onto by Pearson, who acrobatically hooked home from close-range.
The visitors snuffed out any hope of a grandstand Mariners’ finish and there were few sniffs of goal in the final moments for Hurst’s side.
Mariners: McKeown; Parslow, Thomas, Nsiala, Pearson; Clay, Disley (McLaughlin); Pittman, Arnold (Neilson), Mackreth; John-Lewis (Hannah). Subs not used: Walker, Bignot, Doig, Humble
U’s: Clarke; Riley (Meades), Holmes-Dennis, Wright, Mullins; Whing, Rose, Potter, Howard; O’Dowda (Brown), Roberts (Barnett). Subs not used: Crocombe, Long, Ruffles, Collins