United, who were crowned champions last season, are among a number of the country's top teams who have changed managers over the summer.
"It is the most unpredictable Premier League ever and it's all very exciting for the fans," Giggs told The Sun.
"It's a big change here with Sir Alex Ferguson going - but it's also all change at Chelsea and Manchester City and no one really knows what is going to happen.
"There are some really good teams and really good managers battling it out, so it's going to be closer than ever."
United start their Premier League campaign with a trip to Swansea City next Sunday.