Alessandro Diamanti sparkles as Western United complete A-League semi-finals lineup

There is an absurdity to Alessandro Diamanti bestowing his outrageous talent week-in week-out on a near-invisible A-League. It’s like tuning into Neighbours and finding Jack Nicholson sauntering down Ramsay Street or sitting down for a counter meal at a corner pub with a massive Rothko burning into your retinas from where the flatscreen TV used to hang.

It is not simply that Diamanti is a good footballer – that much is obvious for a man crowned the competition’s player of the season – but that he is a beautiful footballer, whose vision and balance, audacity and technique enhances the world around him. His influence on and off the pitch has helped Western United into a semi-final in their debut season, and he has done it by scoring memorable goals, delivering breathtaking passes, and curating the coolest playlists.

Related: David Squires on ... Alessandro Diamanti, perfect marquee signing

Sunday’s elimination final against Brisbane Roar was a typical bravura performance. He was the best player on the pitch by the length of the West Gate bridge. You could not avert your gaze from the endless scheming and gesticulating, hell-raising and peacemaking. Even during the post-match wind down he found himself on telly, whirling his arms around wearing more ink than fibre and belting out the club song like a teenager at schoolies. This is a 37-year old Azzuri veteran.

His lead-up play warranted at least two assists to complement his winning goal (their absence a fitting illustration of the gulf in quality). And what a winning goal it was, a left-footed free-kick that swerved wickedly around the orange wall and dipped with too much force to be contained by Jamie Young’s dive.

Diamanti’s individual brilliance for Western United was in contrast to the collective endeavour that allowed Perth Glory, the weekend’s other victors, to smuggle their way beyond Wellington Phoenix. To the casual observer Wellington were the better team. They attempted 31 shots, eight men in yellow touched the ball more than any individual in purple, and their nimble wide players Liberato Cacace and Reno Piscopo caught the eye with dazzling footwork and a determination to take the game on and break lines.

Glory’s coach, Tony Popovic, was more than just a casual observer, and when he cast his expert eye on the scene he saw something entirely different. At half-time Popovic was asked about the balance of play favouring his opponents. “I’m not sure they had a shot from inside the box,” the Asian Champions League-winning manager responded, with the casual air of a man in full control of his destiny. By the end of the 90 minutes Wellington had completed six shots on target from inside the penalty area, none of which required anything miraculous from Liam Reddy to repel.

Popovic’s opposite number Ufuk Talay, in his black suit, black shirt and black tie, looked every inch the Diego Simeone doppelganger on the touchline, but it was Glory’s performance that epitomised the Argentinian’s cholismo philosophy. Undermanned and out of form coming into the match, Glory had to execute their strategy to perfection to escape with a result. That involved retaining their defensive shape at all times, establishing a formidable barrier on the edge of their own box, and counterattacking directly and at speed. “Effort is non-negotiable” is Simeone’s mantra, but it applies just as well to Popovic.

Despite demonstrating they cannot be underestimated in a one-off contest Glory still head into Wednesday’s semi-final with Sydney FC as underdogs. The Sky Blues have only lost once in the last 15 instalments of this head-to-head, and Perth have struggled all campaign to fashion results against the competition’s better sides, winning just three matches against fellow finalists during the regular season – two of those against Phoenix. Of course, arriving without expectation against the competition’s silvertails plays into Popovic’s hands and another round of collectivist cholismo.

This expectation management is made more intriguing by Sydney’s dip in form. A model of consistency for four years, the premiers can point to just one win from their last eight matches and they have lost three out of six since the restart. This could merely be a blip, worsened by a greater degree of squad tinkering from Steve Corica and a lack of incentive caused by the premiers plate being wrapped up so early. However, the first choice starting XI came unstuck against Western United last time out.

For their part United have just three days to recover from a bruising encounter before they take on Melbourne City, a side that have improved the longer this season has progressed. They have won five of their past eight matches – four of those victories coming against top-six opposition – and they are unbeaten since the debacle to extract them from their home state was resolved. They have also beaten their crosstown rivals three times. United are going to need Diamanti to sparkle brighter than ever if their campaign is to end in glory.