A relieved Graham Alexander praised his Motherwell players for brushing off a last-gasp equaliser and edging past Morton on penalties in the Scottish Cup.
Stephen O'Donnell looked to have ended the Championship side's resistance when he struck from 25 yards seven seconds before the 120-minute mark at Fir Park.
But Markus Fjortoft headed home unchallenged from a stoppage-time corner to secure a 1-1 draw and take the game to a shoot-out.
Liam Kelly saved from Sean McGinty and O'Donnell did win the game when he netted Motherwell's fifth successful penalty.
Alexander, whose side face Stranraer or Hibernian in the quarter-finals next weekend, said: "I'm happy and obviously relieved because it was a real tough night for us.
"The first target is to be in the next round but we could have done things better. I'd also like to acknowledge how well Morton played and made it difficult for us, which we knew it would be.
"We didn't start well, we were a little bit slow in our build-up, but the way Morton set up made it so. We maybe got frustrated with each other and played into Morton's hands.
"We had some really good chances late in the game and when you score so late on you think you've done it but gave a real sloppy set-piece away.
"But I have to give credit to my players, because throwing it away in that final second could have been soul-destroying. But we picked ourselves up and took five great penalties and Liam has made another good save and we're through."
There was a cost when midfielder Allan Campbell went off injured late in extra-time.
"I have just seen him there with a bag of ice on his leg," Alexander said.
"I think that's a first that I have not seen Allan Campbell complete a game never mind a training session. He is a tough boy, fit as anything so fingers-crossed he will be OK for the coming games because he is a massive player for us.
"I think the ice pack is around his thigh area but I haven't spoken to him about it.
"You fear the worst when someone like Allan Campbell comes off because you think he is beyond human. But he probably showed he is actually human."
Morton boss Gus MacPherson was pleased with his players.
"I thought we were excellent, worked ever so hard, competed for the full 120 minutes against a Premiership team," he said.
"I enjoyed watching the performance. Obviously disappointed to lose in that manner but somebody has to lose when it comes to penalties."
