Rio Ferdinand has given Sir 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 26.

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 Rooney's late deflected effort to secure a share of the spoils - and Ferguson admitted United had flirted with defeat.

He added: "We could have lost the game there's no question, they had some chances and at times our defending was a bit haphazard I thought.

"But at other moments we could have won the game because some of the quality of our football was terrific.

"At 1-0 we looked very strong, and were controlling the match and Wayne Rooney was unlucky to be given offside when he was clear through - it wasn't offside.

"They changed the formation back to 4-4-2 got an equaliser and I thought it was a great game of football after that. It was end to end and both teams deserve great credit for producing a game of football like that at this time of year.

"At times we played some fantastic football but in the context of the game Middlesbrough also produced some great moments and it was just a fantastic game."

Ferguson insisted United had showed they will keep fighting every inch of the way for the title.

He said: "The nature of the club is that we never give in and that's a great quality to have at this time of year.

"It sends out a signal to everyone, and our players and fans in particular, that we will never give in. We will be stretching ourselves in every game as long as we can.

"That point could be important, absolutely. Our goal difference is good obviously, but we cannot take anything for granted.

"I said some weeks ago consistency will win us it and I think the most consistent team will do that and I hope that it's us."

Middlesbrough manager Gareth Southgate said the result had thrown open the title race again.

Southgate said: "I'm not bothered who wins but the pleasing thing is that we have shown we can compete with the three best football teams.

"United and Arsenal are better to watch but Chelsea have a resilience. We have thrown it open a bit which is good for the league."

Alves' goals were his first for the club and Southgate was thankful that "lift-off" had finally been achieved.

He added: "From his point of view, and the team and the fans we have been working for lift-off.

"Last week he was bright and that was the first time we have created chances for him. We have seen on the training ground that he's an excellent finisher.

"His finishes here were outstanding, and he has given everyone a glimpse of what he can do."

Southgate said Middlesbrough had come close to inflicting a defeat on the league leaders.

"We had them rattled, we had them on the back foot," he said.

"We responded very well to going a goal behind and right to the end had chances.

"We have played simple but effective football and have asked questions. That is the thing I'm always saying to the players about the top teams - can they defend? A lot of teams don't ask those questions."

Southgate and Ferguson clashed on the touchline briefly but the Boro boss said there was no problem between the two managers.

"I was complaining about one of the decisions and he was saying it was justified.

"I think it's important I don't back down in those situations but I have complete respect for him."