"Unfortunately Rio's still not training and we're trying to give it time to settle," United boss Sir Alex Ferguson has said
"We're managing it the best we can.
"He certainly won't be playing in the next two games but hopefully we'll have him ready for Chelsea next Sunday.
"By that time it will have hopefully settled down and he'll be available for the big one against Chelsea.
"The work we're doing at the moment is geared towards making his back more supple and there's more resilience to the problem.
"The work he does in the gym is important."