However, Rojo is in line to make his debut for the Red Devils in their clash with Queens Park Rangers on September 14 at Old Trafford.
He told reporters: "I am desperate to get onto the field and play because I have not been able to step onto Old Trafford.
"My life has changed a lot. I am very happy to be at Manchester United, a top team in the world, sharing a dressing room with players like Wayne Rooney, Robin Van Persie, Angel di Maria and now Radamel Falcao.
"This is a very important step in my career as a player and as a person. Everything that has happened to me since the World Cup has been a dream."
United have taken just two points from their first three matches of the Premier League season.