With Chris Woakes swinging the bat fearlessly at the other end 48 runs were plundered from the last 18 balls with Buttler running two from the final delivery to bring up his ton and take his side to 302-6. He notched his fifth ODI century from the last ball of the innings. "If Hazlewood and Cummins come back on Sunday it's important that we start well against the aggressive English line-up".
Yet again the conditions defied expectations. "England have been chasing well so it will give them a chance to try and set a total for us".
The slow pitch caused England problems all through their innings and every time a partnership developed, it was cut short. "If you look at my lips, they're pretty dry!"
Morgan said after the game: "It is probably our best win as a group to date".
"The way the game unfolded, I was thinking my way through it and was trying to back it up through the last few overs".
It is tempting in retrospect to view the first 22 overs of the England innings as a phony war, a scene-setter for the brilliance to come, but that would be unfair on Australia's reunited seamers Mitchell Starc, Pat Cummins and Josh Hazlewood.
Following the dismissal of the skipper and Moeen Ali, Buttler came into his own in the death overs with Chris Woakes providing him the ideal support. He was outstanding with bat in hand in the previous match at Brisbane but was overshadowed by Root's contribution.
In all, the pair put 113 for the seventh wicket in only 11.5 overs.
England crumbled against South Africa at Lord's last May, tumbling to 20-6 and scoring just 153, before a collapse of 8-83 saw them slump from 128-2 to 211 all out as they were knocked out by Pakistan in the Champions Trophy semi-finals in June.
Australia were left needing 122 in 16 overs and despite the best efforts of Tim Paine and Stoinis, who cracked a punchy 56, Woakes and Wood closed things out with minimal drama.
Morgan praised the England bowlers and hoped that they will be able to continue in the same vein over the rest of the series.
In truth, the hard work had been done in the previous over by Mark Wood when 30 were required from two.
England celebrate the key wicket of Marcus Stoinis in Sydney.
The partnership was broken in controversial fashion as Wood found Smith's edge which went low to Buttler, who claimed the catch, and after much deliberation the third umpire said that it was out much to the anger of Smith, who thought the ball hit the ground.
England possess ample options with the ball, too - the tourists successfully defending their total of 302-6 despite Plunkett bowling just 1.2 overs due to a hamstring injury, which be assessed on Monday.