Match ends, Morton 2, Dundee United 1.
Greenock Morton overcame fellow Championship side Dundee United to reach the semi-finals of the Scottish League Cup.
Jai Quitongo fired in off the underside of the bar to give Morton the lead.
And Thomas O'Ware headed in Ross Forbes' corner to double the hosts' advantage.
United reduced their deficit in the second half, Nick van der Velden finishing well, but the visitors could not find a leveller.
Morton and Rangers, who beat Queen of the South, will go into Thursday's draw for the last four, with Celtic hosting Alloa Athletic and St Johnstone taking on Aberdeen in this week's other quarter-finals.
Fate can be a curious thing. Dundee United had not visited Cappielow in 20 years but found themselves facing Morton twice in five days.
Both managers insisted the cup tie in Greenock would have no influence on the weekend league meeting in Dundee but a measure of the differing depths of squad was Ray McKinnon's five changes for United and beleaguered Jim Duffy only able to make one switch due to injuries to half-a-dozen key players.
A scrappy first half ensued in which, on a balmy Greenock evening which served up perfect playing conditions - swarming midges apart - the ball was played too long, too often.
Over-hit diagonals seldom make for happy viewing and there were few early goalmouth thrills.
But then Quitongo, 19, lit the game up. He latched on to Ross Forbes' delicate head-flick but still had a lot to do. The striker is strong and athletic - his acrobatic celebration confirmed that - and he powered forward before unleashing a fine strike which seared beyond Cammy Bell. A star in the making, Quitongo threatened twice more after the break.
Moments after the opener, United were beginning to hope it might be another couple of decades before they had to return to Greenock, O'Ware's thumping header at the near post converting Forbes' corner.
The mission for the home side in the second half was to wrap barbed wire around their lead but the plan started to crack.
Van der Velden's low shot across Andy McNeil gave the visitors hope and Blair Spittal then struck a net-bound shot, but somehow McNeil got down to his left to shepherd the ball round the post.
Quitongo limped off with cramp, having given his considerable all, and United's Lewis Toshney came close to scoring.
It was a cliff-hanger of a climax and the scrappy early play was a distant memory. In the end Morton hung on to that cliff edge by their fingertips.
And now a first League Cup semi-final in 37 years beckons for a club who could not, on the night, even fill the substitutes' bench. Fate can be a curious thing.
Morton manager Jim Duffy: "It was a terrific cup tie, two teams giving it everything. We defended brilliantly but our front two, Jai Quitongo and Gary Oliver, gave us an important out-ball and that penetration.
"We were a bit unfortunate once or twice on the counter attack.
"Every single player did themselves and the club proud."
Dundee United manager Ray McKinnon: "Everything was pedestrian in the first half, we had no purpose. It was tippy-tappy without any penetration and we got punished twice.
"I'm really disappointed with that. It's probably the worst we've been this season. We need to be more positive on the ball and put teams on the back foot. Full credit to Morton."
- 18McDonaghBooked at 74mins
- 8ForbesBooked at 90mins
- 9OyenugaSubstituted forMcAleerat 76'minutes
- 24QuitongoSubstituted forNesbittat 81'minutes
- 7OliverSubstituted forTiffoneyat 90+3'minutes
- 6ToshneyBooked at 85mins
- 20van der StruijkBooked at 64minsSubstituted forDonaldsonat 76'minutes
- 14EdjengueleBooked at 70mins
- 10FraserSubstituted forMurrayat 65'minutes
- 23van der Velden
- 11ObadeyiSubstituted forCooteat 84'minutes
- Andrew Dallas
- Shots on Target
Second Half ends, Morton 2, Dundee United 1.
Substitution, Morton. Scott Tiffoney replaces Gary Oliver.
Attempt saved. Caolan McAleer (Morton) right footed shot from the left side of the box is saved in the centre of the goal.
Ross Forbes (Morton) is shown the yellow card for a bad foul.
Foul by Ross Forbes (Morton).
Nick van der Velden (Dundee United) wins a free kick in the attacking half.
Aidan Nesbitt (Morton) wins a free kick in the defensive half.
Foul by William Edjenguele (Dundee United).
Foul by Paul Dixon (Dundee United).
Gary Oliver (Morton) wins a free kick on the left wing.
Lewis Toshney (Dundee United) is shown the yellow card for a bad foul.
Substitution, Dundee United. Alistair Coote replaces Tope Obadeyi.
Attempt missed. Lewis Toshney (Dundee United) right footed shot from the right side of the six yard box is close, but misses to the right.
Attempt saved. Simon Murray (Dundee United) right footed shot from outside the box is saved in the centre of the goal.
Corner, Morton. Conceded by Nick van der Velden.
Substitution, Morton. Aidan Nesbitt replaces Jai Quitongo because of an injury.
Delay over. They are ready to continue.
Delay in match Jai Quitongo (Morton) because of an injury.
Attempt blocked. Simon Murray (Dundee United) right footed shot from outside the box is blocked.