The scoreline after 15 minutes had Phoenix fans rubbing their eyes. Two time A-League champions 0, Wellington 2. It was heady stuff.
Sure, Sydney have struggled this season - they started this match on the edge of the top six, were without injured skipper Alex Brosque and have Asian Champions League commitments - but they had been unbeaten against the Phoenix in the last four encounters and weren't expected to be overly troubled in this game.
Powell opened the scoring in the 12th minute, a neat swivel and finish on the turn after a Michael McGlinchey cross ran free in the area. Watson doubled the score a minute later with a crisp left-footed strike after being set free by a Roly Bonevacia pass.
When Bonevacia, playing in his 50th A-League game, made it three in the 37th minute, the expatriate Yellow Fever contingent were in dream land while the home fans contemplated a possible record defeat for the Sky Blues.
As good as the Phoenix were in the first half, the home side were a shambles, especially defensively. Watson, Powell, Bonevacia and McGlinchey had acres of space, with McGlinchey given the run of Allianz Arena at times. Maybe he was inspired by playing against his former coach Graham Arnold, as the All Whites midfielder had one of his best games of the season.
It helped, too, that the Phoenix were defensively strong. The old firm of Ben Sigmund and Andrew Durante were back together, with the retiring Sigmund making his first start since round seven, and Albert Riera gave his usual efficient display in front of the back four. Sigmund was particularly impressive and showed how much he had been missed.
If the first half was a surprise, the second was also unusual. Wellington fell into the age-old trap of sitting on their lead, gradually falling deeper and deeper as the match wore on. They were hesitant in possession and couldn't often gave it away in the attacking third as Sydney started to find their range.
It meant the Phoenix faced a rearguard action for much of the half, especially after Filip Holosko scored in the 51st minute when Glen Moss failed to deal with a Sydney cross. It set up a tense final 30 minutes but the solidity and experience of Sigmund, Durante and Manny Muscat prevented the home side from coming back into the match.
Sydney FC 1 (F Holosko 51)
Wellington Phoenix 3 (B Powell 12, H Watson 13, R Bonevacia 37).
Halftime: 3-0