Just when Adelaide United seemed unbeatable, Melbourne City may have shown the A-League how to overcome Guillermo Amor's side.
On a weekend set up for teams to make a statement - Adelaide versus City is one of two all top-six clashes in Round 23 - the Reds seemed to wilt under the pressure after moving to the top of the Hyundai A-League table last week.
Nick Fitzgerald's impressive strike in the 71st minute saw the visitors triumph 1-0 at Coopers Stadium, but it was arguably John van 't Schip's tactics that really decided the contest, as Adelaide suffered their first A-League defeat since November 28.
City lined up in a 4-4-2 with a flat midfield quartet of Michael Zullo and Nick Fitzgerald flanking Aaron Mooy and Osama Malik, and the hosts generally struggled to play through the visitors' two banks of four.
While the Reds have hardly been playing defensive football, their past three games - which all ended with wins - saw them surrender the majority of possession to Wellington Phoenix, Brisbane Roar and Melbourne Victory.
On Friday night, City were happy to give Adelaide the ball in the home side's defensive half but Van 't Schip's team worked hard to cut off the passing avenues to the likes of Marcelo Carrusca, Stefan Mauk and Craig Goodwin.
With holding midfielder George Mells having a poor first half, Amor's team struggled to play out of defence, giving the ball away 25 times in their back half before the break.
City only did that 17 times.
It meant City often won possession just the defensive side of the halfway line, and with the speed of Zullo, Fitzgerald and Harry Novillo at their disposal, the visitors were very dangerous on the counter-attack.
City striker Bruno Fornaroli would have been expected to score with his near-post header in just the seventh minute - although Adelaide were seemingly lucky to escape a penalty, as Iacopo La Rocca appeared to deflect the effort away with his hand, while Mooy's free-kick forced a good save from Reds captain Eugene Galekovic in the latter's 250th appearance for the South Australian club.
Carrusca was taken off at half-time due to an injury concern, with Bruce Kamau coming on but the chances continued to come for City, with only some uncharacteristic profligacy - particularly from Fornaroli - keeping the scores level.
The introduction of Isaias for Mells after the hour mark saw Amor's side settle in possession but they deservedly went behind when another City counter-attack ended with Fitzgerald cutting in from the right wing to pick out the top corner of the net with his left boot.
Adelaide finished the match with 57.6 per cent possession but produced just eight shots to City's 14, and there's no doubt other A-League coaches should consider sitting back against Amor's men for the rest of the season.
This was a very impressive performance for City, who notched consecutive clean sheets for the first time in 2015-16.
City moved into second in the table with their win, level on 38 points with Western Sydney Wanderers and Brisbane Roar, while just one behind Adelaide (39).