The duo, both out of contract this summer, have not been offered new deals and they will now be available on free transfers.
There had been high hopes for Powell after he was signed from Crewe Alexandra for £6m by Sir Alex Ferguson in 2012 but a succession of injury problems meant he made just nine first team appearances in four years.
Meanwhile, Valdes was signed by Louis van Gaal in 2015 but the pair fell out after the former was alleged to have refused to play for United’s U21 side.
The former Barcelona man was frozen out at Old Trafford and it was clear that he had no future at the club.
Neither departure comes as much of a surprise to supporters as new boss Jose Mourinho would likely not have had either player in his plans. The hope now is that they are given the chance to rebuild their careers elsewhere.