The experienced centre-back has not travelled to the Ukraine for Wednesday's Champions League group game, with Anderson, Fabio and Wilfried Zaha also not involved
|11/1||Manchester United are 11/1 with Paddy Power to win the Champions League
However, United will be without their 34-year-old centre-back for their second fixture in the group in Donetsk, though Moyes has revealed he would not have taken part in the match even if he was fit.
"Rio has a slight groin problem," Moyes told reporters. "It is nothing serious but I was never bringing him anyway."
The United boss, looking to bounce back from his side's surprise defeat to West Brom on Saturday, will also be without Brazilian duo Fabio and Anderson, while Wilfried Zaha has not travelled either.