The Australian was forced off with a calf injury during the Toffees' Europa League victory over Sporting Lisbon on Tuesday.
His absence further depletes boss David Moyes' options ahead of Saturday lunchtime's Premier League clash against United at Goodison Park.
Everton learned earlier this week that another influential midfielder, Marouane Fellaini, will miss the rest of the season with an ankle injury.
John Heitinga is available after missing the Sporting tie through ineligibility and Steven Pienaar returns to Premier League duty after suspension.
Tony Hibbert (groin), Victor Anichebe (back) and loan signing Philippe Senderos (back) are still out but progressing and long-term absentee Phil Jagielka (knee) is also back in training.
Kick-off is at 12.45pm.
Everton (from): Howard, Yobo, Baines, Distin, Neville, Pienaar, Osman, Arteta, Rodwell, Saha, Yakubu, Bilyaletdinov, Donovan, Vaughan, Gosling, Coleman, Heitinga, Baxter, Duffy, Nash.