Rio Ferdinand has been passed fit for Manchester United’s Champions League quarter final, second leg with Porto.

The England defender has been sidelined since aggravating a back injury on international duty in March.

His last appearance for United came in the 2-0 loss to Fulham and he was sorely missed as Porto came away from Old Trafford with a 2-2 draw last week.

Ferdinand sat out Saturday’s win over Sunderland, but has been passed fit following a workout on Tuesday.

The return of Ferdinand will be a huge boost to United who will be able to pair the center back with Nemanja Vidic.

“The quality he has in his game, it makes a difference when he is in the team,” said Red Devils boss Sir Alex Ferguson.

“It also gets us back to the partnership of Ferdinand and Vidic which has been the cornerstone of great defensive performances this season.

”That’s the difference he’ll make.”