After Warner had battled expertly to compile an unbeaten 70 for the London Spirit to put them in the driving seat in the much anticipated Saturday evening clash in Cardiff, Smith could muster just three as his early dismissal led to a collapse by the Welsh Fire.
Only a spectacular unbeaten 86 from Jonny Bairstow, aided by excellent support from Australian allrounder Chris Green (32no off 21 balls) in a magnificent century partnership, gave the hosts the glimpse of a most unlikely win but London held their nerve for a thrilling eight-run win.
Warner, quite indefatigable at the age of 38 as he scampered every run as if it might be his last, cracked two big straight sixes to go with eight fours off 45 balls, helping the Spirit amass an impressive 5-163 on what he called a "difficult, seamy" surface.
Certainly, it looked hard as Smith, opening up with Bairstow, succumbed on just the fifth ball he faced, his unlovely attempted scoop off Richard Gleeson ending in the hands of fine third-man.
That prompted the home side to implode, slumping to 6-55 with Anglo-Aussie Dan Worrall particularly impressive with his 2-31 off his 20-ball allocation.
But Green, who's been having a fruitful spell with Lancashire this summer, finally proved a worthy partner for Bairstow, hitting a six and a couple of boundaries which seemed to trigger his illustrious English partner to move into his best gimlet-eyed 'Here's Jonny' mode.
Bairstow was stupendous, peppering six sixes and six fours around off 50 balls as the Sophia Gardens crowd reached a fever pitch of excitement near the end.
Warner, who won the player-of-the-match 'hero' award and was hailed as "outstanding" by his Spirit skipper Kane Williamson, had to admit with a smile: "We tried to execute but Jonny was on fire!
"Credit to the way he and Greeny batted, they were superb."
The veteran left-hander reckoned he was still trying to get to grips with the 10-balls-per-end format but recognised the Justin Langer-coached Spirit's win as crucial after they'd lost their opening match at Lord's on Tuesday when he fell cheaply for just nine.
"Got a good bus ride tomorrow," he smiled.
He had been helped during the Spirit's innings by a sprightly cameo from fellow Aussie Ashton Turner, who hit 24 off 14 balls before he holed out to Smith off some impressive bowling from another green-and-gold import Riley Meredith (1-26).
In the day's other men's match, another Australian quick Jason Behrendorff impressed in the Oval Invincibles' nine-wicket home win over Manchester Originals, taking 2-16 off his 15 deliveries, including the key wicket of Jos Buttler.
Phil Salt (41 off 32) became the first batter to pass 1000 runs in the competition in the Originals' 128 before Will Jacks (61) and Tawanda Muyeye (59no) helped ease the Invincibles to 1-129 with 43 balls to spare.
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