Roy Keane admitted Sunderland were "ahead of schedule" after watching his side move into the Coca-Cola Championship's automatic promotion places with victory against Cardiff at Ninian Park.
Substitute Ross Wallace curled home a second-half free-kick to lift the Black Cats up to second place in the table.
Wallace, a 57th-minute replacement for Tobias Hysen, took just quarter of an hour to make the game's decisive contribution after Stephen McPhail had fouled Grant Leadbitter on the right-hand corner of the area.
Sunderland's remarkable rise has arrived on the back of a 14-game unbeaten run since the home defeat to Preston on December 30 and the win in the Welsh capital was the latest chapter in the impressive turnaround since Roy Keane's arrival at the Stadium of Light.
The Black Cats were second from bottom of the Championship with just one win from their opening five matches when Keane was appointed at the end of August but now they find themselves serious title contenders.
Keane said: "I must say we are ahead of schedule but when you look at the bunch of players I have and their spirit and desire to work hard it is not really that hard to believe.
"You have to have hopes and that is the reason why I took the job - because I could see the potential of this huge club.
"Okay, we are fulfilling some of that potential a little sooner than I thought but we just want to get back into the Premiership as soon as possible."
Sunderland could be pushed back into the play-off places when Birmingham host midlands rivals Coventry on Sunday but Keane was unperturbed and expects the top two to change regularly between now and the end of the season.
"It happened to us earlier in the season with Birmingham when we were up there for a few hours and that could be the case again," said Keane. "But there will be ups and downs every week now until the end of the campaign.
"We have a chance of getting promotion and if that is by finishing in the top two then that is fantastic.
"If we have to settle for a play-off place then so be it. We would have taken that a few months ago and we would be ready should that be the case.
"But the good thing for us is that we are going into the end of the season on a good run of results and our play is of good quality, which is very pleasing.
"We are getting results consistently but we are not scraping them, the performance levels are good and hopefully that will continue."
On matchwinner Wallace, Keane added: "He has worked hard again in training this week and I just had a feeling that if I threw him on then he would score - and he did it."
Cardiff manager Dave Jones laid the blame firmly at the door of goalkeeper Neil Alexander for his side's defeat.
Alexander will feel he should have done better than palm Wallace's shot into the bottom corner but he appeared to be caught off guard and still lining up his defensive wall.
Jones said: "He is a shot stopper and it was a shot he should have stopped. Simple as that.
"A mistake has cost us but we made mistakes all over from the goal we conceded to missed chances in front of goal at the other end.
"We had chances in the first half that we should have done better with and there was also another mistake in the lead up to their goal before Neil made his error.
"We said at half-time it could be a mistake that decides it and it is disappointing that we made it. I just wish they had made a mistake.
"It looked like it was heading for 0-0. They had had a go and we had had a go. They had another go and we had another go but unfortunately when they came again it was decisive.
"We had two or three really good opportunities in the first half and we have paid the price for not scoring when we were on top."
That was despite the return of the Championship's top goalscorer Michael Chopra.
The 21-goal striker made an earlier than anticipated comeback after it was initially thought he could be out for a month with the hamstring injury he suffered in the defeat at Derby two weeks ago.
Jones admitted he may have been wrong to rush Chopra back for the game.
He said: "He looked like he had been out for two weeks to be honest but with his record he can always get you a goal and that's why he was in.
"At least we have another week to get him completely right for the next game."