Steven Gerrard admits the blame lies with him after seeing Rangers blow yet another chance to deliver a trophy back to Ibrox.
Rangers saw their 27-game unbeaten record smashed by St Mirren after Conor McCarthy's stoppage-time winner sealed a shock 3-2 win.
The Light Blues' fans fully expected their team to march all the way to Hampden and lift the club's first major trophy in a decade after Celtic were dumped out of the competition in the previous round.
Instead it is Jim Goodwin's Saints heading to the national stadium next month to face Livingston after handing Rangers their first domestic defeat in nine months.
Gerrard made four changes to the team that beat Dundee United and he conceded that he got his team selection wrong in Paisley.
"To call it a crazy night would be respectful to us," said the Englishman, who has now failed in his first five attempts to win a cup competition in Scotland. "Look, we haven't performed well and I'm responsible for that.
"I made all the decision, the tactical and personnel, I tweaked certain things. This is one where I'll take the blame, I'm responsible for it all – because the players have been absolutely first class since the first day of pre-season.
"We've had an awful lot of praise as a group, defensively and offensively. But tonight we just weren't at it. And to concede the three goals in the manner that we did is obviously disappointing.
"But I'm responsible for it. So we have to take what's going to come our way."
It looked like business as normal for Rangers when Connor Goldson fired them ahead early but Saints – who brilliantly nullified the threat of player of the year contender James Tavernier – hit back with two goals from Jamie McGrath.
The visitors mounted a late cavalry charge and levelled with Steven Davis' 88th-minute strike. But credit must got to Saints, who immediately raced forward to snatch victory with McCarthy's goal after Allan McGregor had pulled off a wonder save to keep out Richard Tait's header.
Gers will now have to focus on their Premiership title battle for the time being and Gerrard confessed he will have to act fast to ensure the disappointment does not threaten their 13-point lead at the top.
He added: "It'll be a bit different for us, in terms of the season. I'll demand that we react in the right way. I'm bitterly disappointed because it's an opportunity missed.
"We can't allow the disappointment to spiral. At the moment emotions are running high, after a setback like this.
"But you have a choice in these situations. And you find out a lot about the group, about players.
"I know what I'll be doing. I'll be trying to react in a positive way.
"Of course it will sting. It will hurt. But it's my job to pick them up and make sure they go again."
Goodwin was sent off after losing his cool in the celebrations after the winner with a 'get it up you' gesture.
But there was no hiding his delight after guiding the Paisley side back to Hampden for the first time since their 2013 League Cup success.
The Irishman said: "I was sent off for a gesture but listen, I was just emotional. I was so delighted to win the game late on and I couldn't even tell you what I did.
"I exploded at the end because when it goes 2-2, you do fear the worst. Rangers were pinning us back and we were planning for extra-time and how to freshen us up.
"The boys were dead on their feet and we were hanging on, so to win it like we did was great.
"I am delighted for the boys who got the goals. Overall, it was an immense team performance."
