Last season City came from eight points behind their near neighbours with six games left to land their first Premier League crown.
"There's still a long way to go. We still believe we have a good chance to catch them," Vieira, football development officer at the Etihad Stadium, told talkSPORT.
"It will be more difficult than last season, of course, but we have to give it a go.
"When you look at Chelsea, ourselves and Manchester United, I think all three teams have a chance. Man United are in a really good position but what is interesting in this Premier League is anybody can drop points and the door is still open for us.
"We just have to look at ourselves. We know what we have to do and we will keep fighting."