Jordan Stewart’s injury-time strike sent Linfield into the BetMcLean League Cup semi-finals as Portadown finished with praise for the performance but no place in the next round on a night of drama.
A division now divides two clubs with a rich history of battling it out for the Irish League’s top honours - but there was little to separate the sides on the field of play before Stewart made his mark in the final seconds at Shamrock Park.
His close-range finish capped build-up play between Lorcan Forde, Niall Quinn and Matthew Clarke as Linfield secured a 2-1 victory at the expense of a spirited Ports display.
Both switched the focus to a knockout test still smarting from weekend defeats to former managers in, respectively, David Jeffrey’s Ballymena United and Niall Currie’s Carrick Rangers.
However, the similarities stopped at Saturday’s scorelines given Linfield focus on a title charge compared to Portadown’s pursuit of promotion out of the second tier for a second successive season.
Portadown ambition towards claiming a senior scalp - and providing a statement of intent following a fall from grace off the main stage - suffered a setback on seven minutes.
The high-tempo start by the Blues featured some slick play and Kirk Millar’s floating pass from deep found Stewart, with Declan Dunne stopping the initial shot but Michael O’Connor slotting in the rebound.
Matthew Tipton’s commitment to youth has included continued starting appearances for teenagers Carmichael, Luke Wilson and Gerard Storey and the hosts’ greatest encouragement came from the young guns, along with some marauding runs along the left by full-back Jerry Thompson.
Carmichael displayed clever footwork to cut the ball back late in the first half for Adam Salley but the striker dragged his shot wide on the run.
Linfield hit the frame of the goal twice in quick succession during a bright start to the second half.
The first when Quinn took advantage of the time and space afforded by a back-tracking Portadown backline to fire a drive that bounced off the bar and out of the back of Dunne.
The subsequent corner-kick by Millar was bounced off the upright from a Mark Stafford header.
However, Carmichael was central to a Portadown side with ever-increasing confidence after the interval in a display defiant and determined - and in stark contrast to indifferent league form.
That attacking ambition was rewarded with an equaliser on 69 minutes when Sean Mackle’s corner-kick was flicked on and, after Salley and Adam McCallum attacked the delivery, Carmichael reacted first inside the packed penalty area to convert.
However, the final blow arrived in the final seconds to send Linfield into the semi-finals - and Portadown left to reflect on turning cup positives into league progress.
PORTADOWN: Dunne, Carson, McCallum, Lavery, Salley, Hall, Thompson, Wilson, Carmichael, Mackle, Storey.
Subs (not used): Blair, Neill, Kilmartin, Anderson, Douglas, Robinson, Tipton.
LINFIELD: Carroll, Stafford, Callacher, O’Connor, Stewart (Mitchell, 91), Millar (Forde, 66), Clarke, Fallon, Mulgrew, Quinn, Casement.
Subs (not used): Deane, Moller Nielsen, Doyle, Garrett, Reynolds.
Referee: Lee Tavinder.