Nani says the players still have the belief and ability to win a 20th league title despite the setback against Everton on Sunday.
The Reds let a two-goal lead slip - twice - in an incredible match which ended four goals apiece.
The result has given Manchester City fresh hope ahead of the derby clash on Monday week, a game Sir Alex has labelled "the biggest derby we've ever played."
Nevertheless, Nani remains confident the Reds will still have the last laugh.
"There is anger from the players, of course, because we wanted to win [against Everton]. We're disappointed to lose four goals. But that's football. It can happen sometimes," he told MUTV.
"We have to keep believing in our qualities because we still have a great oppportunity to win the title.
"It's a huge game [at City] - there will be a fantastic atmosphere there.
"We have to keep believing in our qualities because we still have a great oppportunity to win the title."