Grayson said: "Somebody from our club has contacted Rui and he is ok, though obviously it's not an ideal situation.
"All managers who have players out there at the African Nations Cup have the best interests of the players and their families at heart.
"If they want to come back it's entirely up to them. It's hard to comment on something that's happening so far away, but if Rui wants to return and not be involved in the cup, we would more than welcome him back.
"He will do what he thinks is right, I'm sure of that."