The highly-rated winger will officially join United in the summer after Palace secured his services on loan until the end of the season to boost their promotion bid.
Boss Ian Holloway can add Jazz Richards to his squad after landing the defender on loan from Swansea.
But fellow loanee Alex Nimely, from Manchester City, is out with a hamstring injury suffered against Bolton.
Paddy McCarthy, Joel Ward (both groin) and Owen Garvan (knee) are also on the sick list while Kagisho Dikgacoi is on African Nations Cup duty.
Holloway has let midfielder David Wright leave for Colchester and loaned young striker Kwesi Appiah to Yeovil.