Manchester United manager Sir Alex Ferguson has suggested that fierce rivals Manchester City may struggle to get their season back on track if they suffer defeat at the hands of Borussia Dortmund tonight.

The Premier League champions are already out of the Champions League but they will have no chance of qualifying for the Europa League if they fail to get a result against the German outfit.

Ferguson, who has already secured progression into the knockout rounds of the Champions League, believes that City's stars may lose interest in the rest of the season if they are out of Europe completely.

"City need to beat Dortmund," the Daily Star quotes Ferguson as saying. "I don't think losing for a big club is healthy.

"On one hand you can be fresh for the second half of the season and play a fresh team every week, but how do you keep them all happy if they're out of the League Cup and they go out of the European Cup?

"I don't know enough about the City players as I've never worked with any of them, apart from Carlos Tevez. But sometimes players want to play every week and you want to keep the momentum going and the interest going. I don't know if City would have an advantage. I'm not sure it would suit them."

Meanwhile, United take on Cluj in their European group clash tomorrow.