The loss of the fringe Socceroo is a body blow to both player and club, with his standout 2016-2017 campaign for the A-League double winners earning the 26-year-old national team recognition.
He made 32 appearances for the Sky Blues in all competitions last season and his absence poses a dilemma for coach Graham Arnold.
Arnold fielded new signing Paulo Retre - a midfielder - in Grant's right-back role during Thursday night's 2-0 exhibition match loss to Arsenal at ANZ Stadium.
But he may now need to dip into the transfer market to cover for his loss, or potentially switch stopper Seb Ryall out wide.
Midfielder Josh Brillante has also played at right back and Aaron Culver might also be an option.
Grant is recognized as the club's perpetual motion man, covering more kilometers per match than any of his teammates and his loss will leave a huge void.
A positive for the Sky Blues was the standout display of keeper Andrew Redmayne against the Gunners.
His performance, which included a penalty save, was timely with talks between Sydney and Swansea City third-choice keeper Mark Birighitti breaking down over a potential loan deal.