The Blues have replaced departing duo Petr Cech and Didier Drogba with Asmir Begovic and Radamel Falcao, although the pair are the only main signings made by the Premier League champions this summer.
Chelsea's rivals have added more names ahead of the season opener on Saturday, including a summer high of £49 million Manchester City paid for Raheem Sterling, yet Mourinho feels his side do not need adding to.
"It's dangerous," he told reporters when asked about the lack of arrivals at Stamford Bridge.
"I think that saying, is right, the saying that: 'If you stand still, you get worse'. It's right, but the same people can move forward.
"You don’t need to buy 10 players to be a better team. You can be a better team with one or two new players and be a better team, with the same people."
