It looked as if it would be a wipeout when Tomic, the last of the quintet in action at Roland Garros, lost Monday's first set to seeded Tunisian veteran Moez Echargui.
But Tomic, who has been trying to roll back the years for more years than he'd care to remember, came back in style to win 3-6 7-5 6-3 in two pulsating hours.
A decade after he reached a career-high of 18 in the world Tomic is now rarely seen at the grand slams, last competing in a main draw match at the 2021 Australian Open.
His last victory in the main draw at Roland Garros was in 2016,
But, at 33, he is now two wins away from reappearing on the big stage.
His first opponent will be Italian teen Federico Cina, ranked 216. Beat him and he will face the winner of Canadian Alexis Galarneau's match with Brazilian Pedro Boscardin Dias, ranked 194 and 232 respectively.
Like Cina they have never reached the French Open main draw.
Tomic's win was a tonic after four losses.
Dane Sweeny and Alex Bolt, seeded 23 and 28 respectively, suffered surprise defeats. Sweeney went down to Britain's 199-ranked Jay Clarke 6-2 6-2 while Alex Bolt was thrashed by 188-ranked Austrian Lukas Neumayer 6-0 6-1.
Bolt, ranked 138, lost the first set in 21 minutes but got on the scoresheet with the first service game of the second, However, after Neumayer held to love Bolt was broken in a 14-point, six-minute second service game.
Bolt won three points in the next four games as Neumayer wrapped up the match in 47 minutes total.
Christopher O'Connell was beaten 7-6 (9-7) 4-6 6-4 by Argentine Facundo Diaz Acosta, who has a similar ranking.
In the women's event Taylah Preston, seeded 19, lost 7-5 6-3 to Japan's Mai Hontana, ranked 82 places below her at 208 in the world.
Elsewhere 2018 finalist Sloane Stephens beat Carol Lee 6-3 6-2 and veteran David Goffin, at his 14th and last French Open, beat 2018 junior champion Tseng Chun-Hsin 6-3, 6-1.
Six more Australians will join the fray on Tuesday (local time): seeds Tristan Schoolkate (15), Priscilla Hon (23) and Maddison Inglis (31), James McCabe, and, in an all-Australian tie, Storm Hunter plays 17-year-old wildcard Tahlia Kokkinis from Sydney.
Eleven Australians have already earned a main draw place through their ranking with Adam Walton and Emerson Jones joining them via wildcards.
Some of those are warming up elsewhere in Europe and had mixed fortunes.
In the Hamburg Open Alex de Minaur beat Fernando Cerundolo 3-6 6-4 6-3 but Rinky Hijikata lost 7-5 6-2 to local hope Daniel Altmaier.
In Strasbourg Talia Gibson lost 7-6 (7-0) 6-3 to Magdalena Frech but Daria Kasatkina defeated sixth-seed Liudmila Samsonova 7-5 6-3.
AUSTRALIANS ALREADY IN THE FRENCH OPEN MAIN DRAW:
Men: Alex de Minaur (seed), Alexei Popyrin, James Duckworth, Thanasi Kokkinakis, Aleksandar Vukic, Rinky Hijikata, Adam Walton (wildcard).
Women: Maya Joint, Talia Gibson, Daria Kasatkina, Kim Birrell, Ajla Tomljanovic, Emerson Jones (wildcard).
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