Western United are set to play finals in their inaugural A-League season after beating Perth Glory 2-0 at Bankwest Stadium.
Besart Berisha opened the scoring in the 27th minute then secured his brace from the penalty spot in the 52nd.
The win puts Western into sixth place -- level with Adelaide United on 36 points but with a vastly superior goal difference (+10 to -5).
Adelaide have played all their 26 games while Western have two games to come.
Perth had the best early chance 20 minutes into the game, when Bruno Fornaroli attempted a bicycle kick off Neil Kilkenny's free kick but put the difficult chance wide.
Seven minutes later, United struck.
Diamanti took a corner short to Max Burgess, who curled a delightful ball towards the back post.
Perth goalkeeper Liam Reddy came off his line and punched the ball but failed to fully clear it, with the ball ricocheting off Berisha's chest and into the goal.
United doubled their lead early in the second half.
Connor Pain was involved in a clever bit of build-up play, then challenged Perth defender Ivan Franjic for the ball.
Franjic went to ground and caught Pain with his sweeping leg, with referee Chris Beath pointing to the spot.
Berisha coolly slotted the penalty for his 18th goal of the season -- two behind golden boot leader Jamie Maclaren.
Western's night was soured by a knee issue to Josh Risdon, with the Socceroos defender suffering the injury in the first half and later leaving the pitch in the 61st minute.
In the 64th minute, Kilkenny's long-range strike forced a save from Filip Kurto, while the United goalkeeper also claimed Fornaroli's 77th-minute free kick.
Perth, who were already locked in to play finals, had the better of the late chances but were unable to make them count, slipping to their fourth loss in six games since the season restart.