Daniil Medvedev might have to delay his holiday plans a while longer after rediscovering his spark to beat Australia's Alex de Minaur in straight sets at the ATP Finals on Tuesday.

The Russian world No. 4 said he was ready to pack his bags after losing his opening group match to American Taylor Fritz on Sunday, but the 2020 champion produced a serving masterclass to overpower De Minaur 6-2, 6-4.

Defeat for debutant De Minaur means he has no realistic chance of reaching the semi-finals but for Medvedev he will enter his last match against top seed Jannik Sinner with hope.

Medvedev's tennis and attitude on Tuesday was in stark contrast to Sunday when he looked distracted and disinterested and earned a penalty point for smashing a courtside microphone.

This time he was fully focused as he made only 10 unforced errors and conceded only nine points on his serve as he extended his record over De Minaur to 7-3.

"The last match I felt too tired mentally to fight the way I usually do," Medvedev said in a courtside interview.

"So during the match when it doesn't go your way you get frustrated. So I went in to this match thinking if I lose I go home Thursday for sure, good feeling, if I win I still have the chance, also a good feeling.

"I just wanted to hit some shots and it worked well."

On Monday, Alexander Zverev began his bid for a third ATP Finals title by beating Andrey Rublev 6-4, 6-4.

Earlier in the day, Carlos Alcaraz struggled with a stomach issue and looked far from the player who won two grand slams this year while losing to Casper Ruud 6-1, 7-5.

Zverev, who won the finals in 2018 in London and 2021 in Turin, extended his winning streak to six matches following a title run at the Paris Masters.

Rublev is making his fifth consecutive appearance at the finals but hasn't won a match at the event since 2022.

Zverev served nine aces and dropped only 10 points on his serve in 10 service games.

Before the Zverev-Rublev match, Sinnner received the trophy for finishing the year at No. 1 in the rankings.

“There's no better place to celebrate this trophy,” Sinner said as his mom, Siglinde, looked on in tears. “Thanks for all of your support.”

Straight-set loss

India's Rohan Bopanna and his Australian doubles partner Matthew Ebden started their campaign on a losing note, suffering a straight-set defeat.

Bopanna and Ebden were defeated by the Italian duo of Simone Bolelli and Andrea Vavassori 2-6, 3-6 in just 56 minutes here on Monday.

The Indo-Australian pair had defeated their opponents in this year's Australian Open final.

Bopanna, who is appearing in the tournament for the fourth time, and Ebden, struggled to match their Italian opponents, failing to earn even a single break point throughout the match.