Following United's 4-4 draw at home to Everton and Manchester City's 2-0 success at Wolves, 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.
"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."
He added: "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.
When asked whether United can still secure a 20th league title, Nani responded: "Of course.
"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."