Adelaide United midfielder Kristian Sarkies is set to be sidelined for six months after breaking his leg.

The 23-year old, who will join incoming A-League club Melbourne Heart next season, has almost certainly played his last match for the Reds after sustaining the injury whilst playing for the National Youth team on Sunday.

Sarkies will miss Adelaide's Asian Champions League campaign after breaking both the tibia and fibula and will undergo surgery this afternoon.