Reds' central defender Osama Malik has been ruled out for up to four weeks with a hamstring injury.
Malik suffered the injury in his side's 0-0 draw with Newcastle on Sunday.
The 25-year-old was replaced by Jordan Elsey just eight minutes into the match on the weekend.
It is a huge blow for United who currently sit bottom of the table without a win and this week face a red hot Melbourne Victory at Etihad Stadium.
The Victory have not lost to Adelaide at Etihad since 2006.