Philadelphia coach Brett Brown has slammed critics of Australian all-star Ben Simmons as the Sixers face up to the challenge of beating the veteran Toronto Raptors in the NBA playoffs.

Brown spoke up for Simmons and for fellow Australian Jonah Bolden during a media conference call ahead of the all-important game five of their Eastern conference semi-final series in Toronto on Wednesday (AEST).

The best-of-seven series is tied 2-2, meaning a Sixers win would give them the chance to clinch the series at home in game six.

Simmons has been in the firing line from some critics for his performance during this series despite facing the daunting task of guarding Raptors superstar Kawhi Leonard, who dominated Toronto's game four victory with 39 points.