The England striker had been easing himself back into work at Carrington after returning from a warm-weather recuperation break in Egypt, but is now back in full training.
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Manager David Moyes had sent Rooney to Egypt for some warm-weather recuperation work with a United fitness coach with a view to getting him fit for Sunday's clash against Chelsea.
Although the club was hopeful he would be back to face the Blues upon his return, Rooney had been easing his way back into training and was not ready for the trip to Stamford Bridge, where Samuel Eto'o's hat trick helped deliver a 3-1 victory for Jose Mourinho's side.
But the striker was involved in full contact training on Monday - including ball work and tackling - and although he is not thought to be ready for 90 minutes, he is expected to play some part against the Black Cats, who lead 2-1 from the first leg.
"Wayne is really keen to get back into the side and is going full throttle in training," a Carrington source told Goal.
"The medical guys have given him the all clear to play, so it should hopefully just be a case of getting his fitness up to scratch."
Rooney's contract expires at the end of next season and Goal understands that he has repeatedly rejected United's attempts to enter negotiations over a new deal.