Melbourne Victory assistant coach Jean-Paul de Marigny was an interested observer as Bayswater City crushed Subiaco 5-0 in soccer’s National Premier Leagues WA on Saturday.

City maintained their five-point lead with a convincing win at the WA Athletics Stadium where they will face Victory in a Westfield FFA Cup Round-of-32 match on August 20.

Subiaco scored two own goals to gift Bayswater the lead and Bayswater heaped misery on the home side in the second half as Gustavo Giron Marulanda, Brian Farrell and Damien Catalano scored to widen the margin.

Bayswater coach Chris Coyne had been unaware of de Marigny’s presence at the ground until after the match.

“It’s pleasing that they’ve shown the respect to the competition and also to us as a club,” Coyne said.

“The fact that they’ve come has shown the FFA Cup the respect it deserves. We’re pleased that we are playing Victory but we’ve just got to be concerned about ourselves.”

The battle for the NPL WA's last finals spot intensified on Saturday when fourth-placed Sorrento were beaten by Cockburn City and Stirling Lions took advantage with a spirited 3-2 win over Balcatta.

Results shrunk the gap between third and sixth place to just six points with four rounds to play.

Balcatta took the lead early against Stirling through Kris Gate but the Lions' David Micevski scored twice in nine minutes to turn the game on its head. Gate's second levelled the scores at 58 minutes but Phil Arnold's header sealed a Lions victory with 11 minutes to play.

The win brought the Lions within two points of Sorrento, who were beaten 3-1 by an in-form Cockburn.

The Cockerel's Matt Barlow had put his team in front until Sorrento's Todd Harnwell equalised in first-half stoppage time. Cockburn fought to regain their lead and succeeded in the final 15 minutes, scoring through Devon Gibson then Julien Teles to secure their fourth straight win.

Bayswater's victory was not the most convincing of the round as second-placed Perth crushed league-bottom team Armadale 7-0 - the biggest margin of the season to date.

Perth's Mark Doninger scored twice to bring his personal tally to 10 goals in six games and 12 goals over the season. He was joined on the scoresheet by Mark Pritchard, Ash Rosindale, Andreas Theodosiades, Aden Da Luz and Adrian Caceres as Armadale failed to keep a rampaging Perth at bay.

ECU Joondalup came alive late in the match to earn a 5-2 victory over Inglewood United.

It looked to be an even contest after David Foster's goal was cancelled out by Inglewood's Ryan Clarke. Inglewood hit the ground running in the second half, taking the lead through Abdul Sesay within three minutes. But Joondalup's Stuart Montgomery equalised in the 70th minute and then Joondalup took full control, scoring through Joe Smith and twice through Tommy Amphlett to tie up the win.

The match between Perth Glory and Floreat Athena was postponed due to poor pitch condition caused by heavy rain and has been rescheduled for 7:30pm at E&D Litis Stadium on Wednesday.​