Nani has admitted a lack of concentration was to blame for pitching Manchester United into the most important derby clash of Sir Alex Ferguson's career at the Etihad Stadium next Monday.
Ten minutes from time at Old Trafford yesterday, most United fans were dreaming of the elation at retaining their crown at the home of those troublesome "noisy neighbours", which would have been the prize for beating Manchester City.
Now, barring improbably large victories in their final two games, Ferguson and his players know that, not only will they surrender top spot if they lose, there will be nothing they can do to alter the situation should City win their final two games.
And for that, United only have themselves to blame.
"There is anger from the players," said Nani.
"The concentration was not the best in the last few minutes - that's why they were able to create chances and score goals.
"We had a lot of possession and played some fantastic football in attack. But we conceded too many goals and we're not happy about that."
Some in the United camp have been quick to try and limit the damage by claiming that, at the beginning of January, after successive defeats to Blackburn and Newcastle, hands would have been bitten off to approach this game with a three-point advantage.
It has also been pointed out that United began their surge by beating City in an FA Cup tie where they established a three-goal lead.
However, for every positive, a negative can be found.
That Cup tie, for instance, ended with shredded nerves from a United perspective as City fought their way back to 3-2, despite the additional handicap of being reduced to 10 men due to Vincent Kompany's harsh dismissal.
And, while United's form to Easter Sunday was almost flawless, then have won only once in three games since and the defensive frailties again exposed by Everton are unlikely to be sorted out fully in a week, no matter how much work is done on the training ground.
For virtually the first time since he ruptured cruciate ligaments in December, United have cause to lament the absence of skipper Nemanja Vidic, knowing the Serbian was also missing when City inflicted that morale-sapping 6-1 defeat at Old Trafford in October.
Vidic is not available, though, so Ferguson has to work with what he has.
Such was the poor performance of Rafael at right-back against Everton that a change is virtually certain.
Yet Phil Jones has been equally loose in his defending recently and Chris Smalling would be a better bet if it were not for the fact he has not started a Premier League game since January.
There has to be a question mark over Ferguson electing to start with two wide players, as he did in that first traumatic Premier League derby of the season, especially as he cannot allow his team to run the risk of Paul Scholes and Michael Carrick being outmanoeuvred in central midfield by Yaya Toure.
"Of course," said Nani, when asked whether United can still secure a 20th league title.
"We have to keep believing in our qualities because we still have a great opportunity to win the title.
"It's a huge game [at City] - there will be a fantastic atmosphere there.
"It will be a difficult game, but if you want to win the league you cannot think about the atmosphere or the opponents, we must just think about the way we play and try to win the game."
However, for all the forceful words of positivity, together with the looming presence of Carlos Tevez, it is that 6-1 scoreline which provides the backdrop to next Monday's fixture, the elephant in the room which underlines what City are capable of if United do not get it right.