The Blues dominated out of the blocks early against a listless Sydney on Thursday night.
But an extraordinary 12-goal, 75-point third quarter featuring a run of six unanswered majors delivered Dean Cox's Sydney a 20.12 (132) to 10.9 (69) win in front of 40,372 fans at the SCG.
The nature of the fadeout puts early pressure on Carlton and coach Michael Voss.
Sydney paid a king's ransom to secure Curnow in last year's trade period, and Will Hayward and Florent were both forced out of the club.
There was no love lost between Curnow and his ex-teammates, nor Hayward and Florent and theirs, with spot fires throughout - and a huge melee after Curnow's first goal.
Florent will likely face scrutiny over a stray knee to the head of former teammate Isaac Heeney as he leapt over the Swan in the second term.
Heeney was assessed for concussion but returned and was dominant with two goals and 20 touches.
Curnow was well held by Jacob Weitering, before snagging three second-half goals.
An inspired third-quarter burst from Justin McInerney (three goals, 29 disposals) helped turn the tide Sydney's way.
Errol Gulden (27 touches) and Chad Warner (20) grew into the game and Joel Amartey (three goals) and Matt Roberts (two goals) were among 12 individual Sydney goal kickers.
Tom McCartin kept Blues spearhead Harry McKay goalless.
Carlton midfielders Sam Walsh (32 disposals), debutant Jagga Smith (27 disposals) and Cooper Lord (26) impressed while ruckman Marc Pittonet snagged three goals and recruit Ben Ainsworth jagged two.
Carlton's Brodie Kemp dribbled through the opening goal from a tight angle before Hayward silenced the crowd with his first goal against his former club.
Sydney were nervy in the first quarter, trailing by 11 at quarter-time but finally drew blood eight minutes into the second term.
But Carlton responded and led by 10 at half-time, then 16 early in the third term.
Heeney, Errol Gulden and Warner came to life in the third term.
Back-to-back McInerney goals, and Logan McDonald's first after being sent forward, got the Swans back in it.
Then Sydney put the foot down.
Heeney put Sydney in front before Curnow finally nabbed his first goal - and tempers flared in the aftermath with a melee breaking out.
The goals flowed from there for the Swans who turned the third quarter into a 40-minute affair and led by 39 at three-quarter time.
The fourth quarter proved merely damage limitation for Carlton, who conceded another six goals.
Carlton's Adam Saad (hamstring tightness) was pulled in the fourth term.
The Blues have a quick turnaround to face Richmond on Thursday and Sydney next face reigning premiers Brisbane at the SCG next Saturday night.
