MELBOURNE, AUSTRALIA -- Frances Tiafoe had never played a No. 1, had never beaten anyone in the Top 5, and now he'd just won a tiebreaker against Novak Djokovic to level their second-round match at the Australian Open.

He nodded and motioned for more noise before plonking down in his courtside chair and saying what everyone watching already knew: 鈥淚 love this. ... I love it!鈥

That lasted right up until the pivotal moment in the fourth set, serving at 3-all, 30-all, when he walked to the side of the court to get a towel, dry his face, and didn't resume play before the countdown clock ran out. He was given a time violation by the chair umpire, and docked a serve.

He lost that game, and didn't win another.

The 23-year-old American, quarterfinalist here two years ago, threw everything he could at Djokovic. But it wasn't quite enough to beat the eight-time Australian Open champion, who won the 3 1/2-hour afternoon match 6-3, 6-7 (3), 7-6 (2), 6-3.

鈥淚 felt like that kind of broke the match, honestly,鈥 Tiafoe said. 鈥淎nd he ran off with it.

鈥淗ats off to him, but that was a terrible ending to the match, to such a high-quality match.鈥

Tiafoe shook his head after finishing the match with a double-fault, then jogged to the net to embrace Djokovic. He'll take plenty from this. He said he knows he can compete at this level.

鈥淗e pushed me to the very limit,鈥 Djokovic said. 鈥淗e's a very quick player. It's unpredictable what comes next ... I'm really glad to overcome such a battle.鈥

Djokovic served 26 aces, Tiafoe 23. Djokovic had the edge in terms of winners (56-49).

After assessing the stats, Djokovic said he couldn't remember serving more aces, or seeing more serves pass him, in a match in a long time.

鈥淐redit to him,鈥 the 17-time major winner said, 鈥渇or forcing me to feel uncomfortable.鈥

Djokovic also agreed in his on-court, post-match interview that Tiafoe got a tough call. It was hot and sunny - the temperature peaked at 32 degrees Celsius (90 degrees Fahrenheit) - and Tiafoe had just lost a long rally.

鈥淭hose kinds of things are just unlucky,鈥 Djokovic said. 鈥淗e deserved to have the first serve.鈥

Tiafoe later said he was glad Djokovic acknowledged it, but he still thinks there needs to be 鈥渃onversations鈥 about allowing more time between points while COVID-19 pandemic restrictions mean ballkids can't hold the towels for players.

鈥淐ould I have handled it better? Yes,鈥 Tiafoe said, answering his own question. 鈥淵eah, I mean, that just broke me. I'm out there battling world No. 1, and like he needs any more help, you know.鈥

Djokovic will play another American in the third round after No. 27-seeded Taylor Fritz who held off Reilly Opelka 4-6, 7-6 (6), 6-7 (4), 7-6 (5), 6-2.

Dominic Thiem, who lost the final last year to Djokovic but went one better to win the U.S. Open, took a short route to the third round with a 6-4, 6-0, 6-2 win over Donimik Koepfer and will next play unpredictable Australian Nick Kyrgios.

Another U.S. Open champion, Naomi Osaka, needed only an hour to sweep Caroline Garcia 6-2, 6-3.

Serena Williams kept her bid for a 24th Grand Slam singles title on track, making only 11 unforced errors as she defeated Nina Stojanovic 6-3, 6-0.

But a 21st trip to Melbourne Park ended painfully for her older sister, Venus Williams.

The 40-year-old Williams, a seven-time major winner making her 88th Grand Slam main draw appearance, was down 5-1 in the opening set against Sara Errani when she landed awkwardly on her ankle as she approached the net for a volley. She fought back tears before receiving treatment on the ankle, and gamely continued, hobbling between points, before losing 6-1, 6-0.

Two top 10 players went out of the women's draw: 2019 U.S. Open champion Bianca Andreescu, coming back from 15 months out with injury, was beaten by Hsieh Su-wei of Taiwan and ninth-seeded Petra Kvitova, a two-time Wimbledon champion and the 2019 Australian Open runner-up, lost to Sorana Cirstea

鈥淚t's strange,鈥 Hsieh, who is ranked 71st and has a history of inconsistency, explained of her 8-2 record against top 10 players. 鈥淚 normally feel more excited to play with better players.

Second-seeded Simona Halep narrowly averted an early exit, rallying from 5-2 down in the third set to beat No. 72 Ajla Tomljanovic 4-6, 6-4, 7-5.

French Open champion Iga Swiatek, seventh-seeded Aryna Sabalenka and 2020 Australian Open runner-up Garbine Muguruza all advanced, along with Ann Li, a 20-year-old American who beat Alize Cornet 6-2, 7-6 (6).

No. 11 Denis Shapovalov, No. 14 Milos Raonic and No. 20 Felix Auger-Aliassime all advanced, keeping Canadian interest alive, and sixth-seeded Alexander Zverev completed the night session on Rod Laver with a 7-5, 6-4, 6-3 win over American qualifier Maxime Cressy.

Crowd numbers lifted on a nice, sunny day, hitting 19,900 across day and night sessions - a maximum of 30,000, or roughly 50% of capacity, are allowed through Melbourne Park under COVID-19 restrictions.

There were thousands in John Cain Arena, known by Kyrgios and his fans as the Peoples' Court, to watch the mercurial Aussie save two match points before beating No. 29 Ugo Humbert 5-7, 6-4, 3-6, 7-6 (2), 6-4 in a rollicking night cap full of turns and twists.

鈥淚 don't know how I did that, honestly,鈥 Kyrgios said, thanking the parochial, vocal crowd. 鈥淚t's one of the craziest matches I've ever played.鈥

AP Sports Writer Steven Wine in Miami contributed to this report.