Sunday's 14:00 GMT kick-off at Old Trafford precedes the international break and the arrival of new head coach Ruben Amorim.
Ruud addressed the press at Carrington and discussed Amad, who was withdrawn during the 2-0 victory over PAOK in the Europa League, after scoring both goals in the second half.
There is also encouraging news on Kobbie Mainoo, as the midfield options are increasing on the back of Thursday's triumph.
"Amad was assessed," declared van Nistelrooy. "We're still working on him, to get him ready for Sunday. Hopefully, it will work.
"Kobbie is also progressing in his injury, he’s making the right steps, but is not yet with the team, though.