Rooney feels United's summer signings of Bastian Schweinsteiger, Morgan Schneiderlin, Memphis Depay and Matteo Darmian will give the club extra quality and consistency they need to challenge for the Premier League title.
He said: "I am excited about the season. It is a big season for us.
"I think we have enough quality now to challenge for the title.
"At times last season we were very good, particularly in some of the big games. Now we have added four quality players and they will help us be a bit more consistent and give us a real chance of the title."