Robben: Man Utd still strong without Ronaldo
Despite United's recent problems, the 26-year-old is expecting them to provide as tough a challenge as ever.
Asked if he felt United had become weaker since he left Chelsea and English football, Robben said: "No, I don't think that. They are a good team and that was seen in their results last year.
"Obviously Cristiano Ronaldo has left and he is a great player, but there are other players (at United) as well."