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Federico Macheda on stand by as Manchester United wait on Wayne Rooney injury update

Sir Alex Ferguson is ready to turn to teenage striker Federico Macheda if the ankle injury sustained by Wayne Rooney against Bayern Munich forces the 34-goal forward out of Manchester United’s title run-in.

Rooney, who left the Allianz Arena on Tuesday night on crutches and wearing a protective boot on his lower right leg, is set to discover the full extent of his injury today.

The 24 year-old was helped off the pitch by club doctor Steve McNally and kit-man Albert Morgan after being injured in a last-minute challenge by Bayern forward Mario Gomez.

United are due to fly back to Manchester this afternoon and by that stage, Ferguson and his staff should know the likely length of any Rooney lay-off.

If Rooney is forced to spend time on the sidelines, he will join crocked attacking team-mates Michael Owen and Danny Welbeck on the casualty list.

That would leave Ferguson to rely on just Dimitar Berbatov, Mame Biram Diouf and Macheda for the decisive games of United’s season.

But Italian youngster Macheda, who burst onto the scene almost a year ago with crucial goals against Aston Villa and Sunderland, has returned to full fitness after a season blighted by calf injuries.

And Ferguson admits that the 18 year-old can have a big impact again for United in this campaign’s run-in.

Ferguson said: "Macheda has had a terrible season with injuries, but he came back on Saturday (against Bolton) and I am delighted about that.

“That’s because, without question, he is one of the most exciting young strikers I have had in my time at Manchester United.

"His ability about the box for a young player is outstanding."

United now face a stern challenge against Bayern in next Wednesday’s Old Trafford second-leg after emerging from Munich with a defeat.

The Germans will be boosted by the return of fit-again Arjen Robben and Germany midfielder Bastian Schweinsteiger, who was suspended for the first-leg.

But United midfielder Darren Fletcher insists Ferguson’s team remain alive in the tie.

He said: “It's not insurmountable. Although we’re disappointed to have lost two late goals, 2-1 isn’t the worst result in the world. We now know what we have to do at home.

“We certainly respected Bayern before this match and we’ve still got great respect for them.

“They’re a very good side. You don’t play any bad sides in the quarter-finals of the Champions League.

“We’ve learned a lot about Bayern and about ourselves and we’ll take all that into the match at Old Trafford next Wednesday.”

© Telegraph.co.uk