Australia's soaring tennis men are on the verge of another crack at Davis Cup finals glory after winning their second group-stage tie in just three days with a 3-0 whitewash of an ailing Czechia outfit in Valencia.

Lleyton Hewitt's team, runners-up in the World Cup of men's tennis for the last two years, is now odds-on to make the 'final-eight' week in Malaga in November after following up their 2-1 win over France with a much easier outing against the injury and illness-hit Czechs.

Thanasi Kokkinakis, again entrusted with the tricky number two singles spot by captain Hewitt, came up trumps once more on the indoor hard court, maturely dealing with the erratic firepower of rising teenage star Jakub Mensik in an impressive 6-2, 6-7 (2-7), 6-3 victory first up.

The Czech challenge then crumbled after just eight minutes of the second rubber when their number one, Tomas Machac, who had been forced to retire with cramp during his loss to Carlos Alcaraz in Wednesday's loss against hosts Spain, again pulled out, this time with injury, against Alexei Popyrin.

To complete what Hewitt felt was "a perfect day", his trusty doubles pairing of Matt Ebden and Max Purcell made short work of Mensik and Adam Pavlasek 6-4, 6-2 to improve their Davis Cup record together to 8-1 and seal the vital win.

"Thanasi was fantastic in the first match," said Hewitt, who was justified in choosing him ahead of the higher-ranked Jordan Thompson as the world number 78 provided the ideal follow-up to his straight-sets win over another rising star and higher-ranked opponent Arthur Fils in the French tie.

Mensik, a 19-year-old with a big future, provided plenty of trouble as he battled back to nick the second set after Kokkinakis had served for a straight-sets win, but Kokkinakis regrouped and was then immaculate on his delivery as he bombed down a total of 19 aces while controlling the decider.

The subsequent battle between the two number ones turned into a farce as it immediately became obvious that Machac, moving stiffly and with right calf heavily strapped, shouldn't have been playing at all as he needed courtside medical attention after losing just the first game.

At 15-30 down on his own serve in the second, he then offered a resigned hand to Popyrin, gifting the Australians victory after just nine points.

The reason Machac was forced to play was because the Czechs, who had only four men in their team, had been hit by another match day blow when their number two singles man Jiri Lehecka was forced out with illness.

The victory put Hewitt's team in a powerful position to reach the eight-team finals week after a second group B victory, with a tie against the Alcaraz-inspired hosts still to come on Sunday.

If Spain beat France, the Aussies' ticket to Malaga will be guaranteed.

There's still a slim chance of a French whitewash of the hosts, followed by Spain beating the Czechs 3-0 and Hewitt's crew being trounced 3-0 by Alcaraz and co on Sunday, which could scupper Australian dreams.

AAP