Australian No.1 Alex de Minaur has withdrawn from this week’s Adelaide International, citing a rib injury.

The 20 year-old was the top seed at the tournament after world No.2 Novak Djokovic withdrew at the weekend.

De Minaur had a big week of tennis at the ATP Cup, where he pushed world No.1 Rafael Nadal to three sets in Australia’s semi-final loss, but it is not known whether the injury is serious enough to cast any doubt about his Australian Open participation.