SYDNEY: Daniil Medvedev and Alexander Zverev both clocked impressive victories on Tuesday as they ramped up preparations for the Australian Open by keeping Russia and Germany on track at the ATP Cup.

US Open champion and world number two Medvedev bounced back after being shocked by Frenchman Ugo Humbert at the weekend to crush Australia's Alex de Minaur 6-4, 6-2.

Third-ranked German Zverev, meanwhile, came through a workmanlike 6-4, 6-4 clash against American Taylor Fritz, his second straight win of the new season.

Seventh-ranked Italian Matteo Berrettini also tasted victory, responding after he was upset by De Minaur on Sunday to battle past Humbert 6-4, 7-6 (8/6).

Medvedev, who will be the second seed at this month's Australian Open after defending champion Novak Djokovic confirmed his participation, said afterwards he had taken painkillers before the match, because of soreness.

"Before the match, to be honest, I was not feeling great," he said.

"I didn't tell it to anybody from my team because I had to go out there and try to win. I took some painkillers and was able to play some good tennis."

He said he was sore after a near three-hour singles match on Sunday followed by a tough doubles rubber.

His win sealed the tie 2-0 for the defending champions' second group win after Roman Safiullin earlier ground past James Duckworth 7-6(8/6), 6-4 in the other singles match.

Germany also enjoyed a win with Jan-Lennard Struff giving them a 1-0 lead with a gutsy 7-6 (8/7), 4-6, 7-5 victory over big-serving John Isner, who smashed 34 aces, before Zverev wrapped up the tie.

"In general, it was at a good level for second match of the year, a high intensity and hard hitting," said Zverev. "Most important is that Team Germany won."

The victory kept Germany's ATP Cup hopes alive after they lost to Britain in their opener, with only the top nation from each of the four groups progressing to the knockouts.

Last year's runners-up Italy suffered a disappointing defeat on Sunday against Australia, largely down to Berrettini losing in straight sets to De Minaur.

But he made amends against Humbert, winning 85 percent of his first-serve points.

"A really tough match, especially in these conditions. He's a great server, a tricky player, a lefty," said the Italian, who dominated with his serve, sending down 18 aces.

"It's a big weapon that I have and when it is working like this, it helps me a lot."

World number 10 Jannik Sinner set Italy on their way, defeating France's Arthur Rinderknech 6-3, 7-6 (7/3) in the opening singles, rallying from a break down in the second set.

"It's never easy playing against him, it was the third time already. The first set I was under control. In the second set I dropped a little bit of intensity," said Sinner.

Rinderknech defeated Sinner on clay in Lyon last year, and appeared primed to push for another upset, but one error allowed the Italian back on serve and he made no mistake from there.

France are now 0-2 at the tournament, having also lost to Russia.

In the day's other tie, Canadian world number 11 Felix Auger-Aliassime edged Britain's Cameron Norrie, ranked a place below him, 7-6 (7/4), 6-3 after teammate Denis Shapovalov crashed to Dan Evans in straight sets.