The August 26 Old Trafford meeting comes amid suggestions Jose Mourinho is playing mind games with new United boss David Moyes as Chelsea bid to recruit striker Wayne Rooney.
"It's very important for us psychologically to start the season well," said Ivanovic in Jakarta on Wednesday, ahead of Thursday's final match of the Blues' Asia tour.
"I think it can give us extra confidence and after that we can play game by game. The season is very long. We have to be ready for every challenge."
Asked specifically about the Old Trafford contest, Ivanovic said: "It's very important, more mentally, because it's the beginning of the season.
"That game will not decide who is going to be champions, but it will decide a lot of things about the confidence and about the team."
After six matches against United without a win, the momentum in the fixture has turned in the Blues' favour, with three wins and a draw in the last four matches.
Ivanovic knows, though, that small incidents can prove crucial in such a clash.
"Every game against the big teams is different," he said. "Small things decide the games. We have to be ready for that."
Ivanovic anticipates the tussle for the title will make the Premier League "one of the toughest Premier Leagues of the last couple of years".
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