Castro's deflected first-half goal was followed by substitute Keogh's clinical second-half strike on Friday night at Coopers Stadium.

The Perth pacesetters' comprehensive triumph extends their gap atop the table to nine points ahead of weekend games.

But coach Tony Popovic says any talk of a certain Premiers Plate collection is premature.

"The reality is ... it's not done," he said.

"But the consistency is really down to the players.

"They showed these type of performances early in the season as well ... but they have been able to consistently produce that and, I feel, improve along the way."

Fifth-placed Adelaide, now five games without a win, could slip to sixth by the end of the round with their finals place in peril.

"I know it's dangerous (position)," Adelaide coach Marco Kurz said.

"But I still believe and trust in the boys."

The Reds were bossed by the Glory, who made Adelaide pay for two blunders.

Castro rewarded Perth's early dominance in the 35th minute, though with a dose of fortune.

After a sloppy clearance from Adelaide goalkeeper Paul Izzo went straight to Perth's Ivan Franjic, the Glory right-back found Castro 15 metres out.

The Spaniard turned onto his right boot and fired a shot which was headed wide but deflected off United defender Scott Galloway into the net.

Perth, with a fluency befitting a team with just one loss in 22 rounds, were causing Adelaide problems all over the park - their halftime lead could have been more but Izzo denied attackers Chris Ikonomidis and Joel Chianese with diving saves.

Adelaide's fate was sealed in the 70th minute when captain Isaias turned over possession in his defensive half - his long, sideways pass was smartly intercepted by Keogh.

The Irishman dashed forward unchallenged and, when 15 metres out, expertly slotted into the right-side of the net for his 13th goal this campaign.

Australian Associated Press