Alan Pardew praised his team for forcing the win on Tuesday as five goals were shared with Hartlepool.
Talk of Wembely has gathered momentum this week, and the gaffer was happy to negotiate a tricky home fixture against a battling visiting team.
"The result pleased me more than anything because we took our eye off the ball and you can't do that. It's a big game for a lot of these young players here on Sunday, a big game, as much as we tried to get it out of their minds, obviously it hadn't," he said.
"The players who have been there and done it stood up a little bit. Fonte is a top player and you'd think he was just about to play in the semi-final of the cup against Liverpool with his attitude today. Some of our younger players took their eye off the ball, not much, just ten percent maybe, but it was enough to put in a performance that was disjointed and not quite right."
The manager shouldered the responsibility for the indifferent start from Saints which saw them concede early on, but felt that his side always had a chance of turning it around with the players at his disposal.
"Tactically we set up with a different system tonight, I made a mistake so there were a lot of errors tonight, but the most important thing for us is that we won.
"I was actually trying to do change it before we scored, but didn't get there in time! You just have to hold your hands up sometimes when it doesn't work, but Hartlepool had nothing to lose tonight.
"They came here fighting for their lives, flying out of the traps, got around us, were lively, I don't think it would have mattered if we played 4-5-1 or 4-4-2 they were going to cause us a problem as we weren't ready.
"There were a lot of variations tonight and that happens in football, but we have got goalscorers in our team and they got us out of jail tonight. Barnard sniffed one out and Rickie is going to punish you if you make a mistake like that and Papa got us out of trouble too.
"We have got resilience. If this team is going to be the Man Utd of this division then you have got to really concentrate in every game, you've got to focus in every game. You can't look at the next game and we did that tonight, but as long as we learn from that then the winning mentality in the dressing room will see us home."
Pardew can now allow himself to fully focus on Sunday where he is hoping to reward the hoards of Saints fans making the journey to North London.
"The most important thing is that we focus on the game and that we do justice to 44,000 people who are paying a lot of money, not just for their tickets, going beyond the call of duty to get there when the train service is up to God knows what. So we have a duty to them, we have a winning mentality in the dressing room, we have no divine right to win it on Sunday and we have a few players unavailable so that gives the opportunity to a few of our squad players who as I have just said have had a terrific attitude.
"We've hit an injury crisis at a bad time for us really as it is the nuts and bolts of the season, and of course we have four or five players who aren't available. So now we have to fall back on the spirit of the squad which has been strong, I have to pay tribute to the players that I inherited here who haven't lost their focus. Simon Gillett has probably got a chance of playing on Sunday and he hasn't really been given a chance of playing by me, this is how football works out sometimes.
"It's funny how it might fall on the plate of someone who hasn't really featured much, and I have no problem with that. I'm looking forward to it and the team are obviously looking forward to it, they showed that tonight!
"Whatever happens on Sunday we have a massive game on Thursday, so we can't look to the next game, it's got to be game in front of you and that's where we fell down tonight. Our fans were terrific, they stayed with us on a difficult evening for us mentally, but we got through."
