Rio Ferdinand has given  Alex Ferguson another defensive headache after leaving the Riverside with his foot in a protective case following Manchester United's 2-2 draw with Middlesbrough.

United can ill afford to lose Ferdinand for long with fellow centre-back Nemanja Vidic out for three weeks and some crucial matches coming up in the Premier League and Champions League.

The draw with Boro sees United just three points ahead of Chelsea, and they have to face Arsenal next weekend before going to Stamford Bridge on April 26th.

Ferdinand limped off during the match and left the stadium with his foot in a plastic case, as a precaution.

Ferguson said: "Hopefully it's not serious with Rio but he was limping for too long.

"The danger was to keep carrying on with him when he was limping he was not playing at his full performance level."

It looks unlikely that Ferdinand will play in the Champions League second leg against Roma, especially with Gerard Pique impressing Ferguson as a replacement for the England defender.

"Pique came on and did absolutely terrific, he was absolutely marvellous and I think that helped us actually," added Ferguson.

United had taken the lead at an icy Riverside courtesy of Cristiano Ronaldo's 37th goal of the season but two goals from Brazilian striker Afonso Alves put Boro ahead.

It was left to Wayne