Diego Castro scored twice as Perth Glory inflicted a 5-0 hammering on sorry Adelaide United in Friday's A-League encounter.

Champions United have endured a miserable campaign and an hour delay to kick-off due to soaring Adelaide temperatures merely acted as a stall to a rampant performance from Perth, who move fourth.

A poor own goal from Iacopo La Rocca in the 15th minute set the tone for the home side, who were 3-0 down at the break as Castro and Andy Keogh scored two goals in eight minutes towards the end of the half.

Any slim hope of a comeback was extinguished just 35 second after the re-start as Adam Taggart volleyed home from close range to extend Perth's lead.

Riley McGee went close to a consolation for Adelaide when his deflected strike arrowed narrowly past the post, but Glory piled on more misery two minutes from the end when Castro guided home Aryn Williams' cross.