Scott Sellars’ team were cruising at 6-2 up but three goals from a spirited Oldham side in the last few minutes set the nerves jangling.
After a lively and even opening spell, it was City’s Bradley Robinson who opened the scoring in some style after nine minutes, ending an unchallenged diagonal run with an unstoppable shot that tore past Routledge.
Watched by father Frank in the stands, Harry Bunn doubled the lead after 34 minutes, pouncing from close range when the Oldham keeper failed to hold onto a shot from Adam Drury.
However the home side came right back at City and were level before the break. Tarkowski headed a free kick beyond Karius on 36 minutes, and when the City keeper’s punched clearance was drilled back in, Matt A Carr touched it home through a crowded six yard box.
Whatever was said in the dressing room at half time seemed to do the trick, with Harry Bunn getting his second just two minutes after the break. Luke Coulson opened the lead up just afterwards with a fine angled shot that went in off the post, and then Alex Henshall made it 5-2 when he stretched to poke home a loose ball after 51 minutes.
Good work from Bunn allowed Henshall to get his second on 75 minutes, but Oldham were not done and drew one back when Burns drove a first-time shot past Karius. A scramble in the box ended with the ball in City’s net, which the referee finally confirmed as a goal after seemingly thinking about giving a penalty for handball.
There was even more drama as Oldham spectacularly reduced the arrears through a long range free kick from Fitzgerald that looped over Karius. The home side, watched by first team manager Paul Dickov, threw everything they had at City in the dying seconds but there was to be no more shocks and City now face Nottingham Forest away on a date yet to be confirmed in January.