Alexander Zverev is through to Round 4 of the Australian Open after a straight-sets victory over Radu Albot on Friday. But the third seed admitted there were “struggles on the court” during his 6-3, 6-4, 6-4 win at Melbourne Park as he looks to secure a first Grand Slam title that many felt would have arrived by now. Zverev has been impressive in his three wins so far in the tournament — where he has yet to drop a set — as he shapes up to a possible quarter-final with 20-time Grand Slam champion Rafael Nadal. “I think Radu is in great form, he's played five matches so far, so he is obviously playing well, feeling the ball well,” said Zverev who is into the second week in Melbourne for the fourth year in a row. “I am happy to be through in three sets. I had my struggles on the court today, I didn't feel perfect, but who is perfect? At the end of the day I won and I'm happy about that.” The German needed just a single break of serve in each set to set up a last-16 clash against what is likely to be more formidable opponent in the shape of 14th seed Denis Shapovalov. Albot, who plays much of his tennis on the second-tier challenger circuit, was shaking his head at the quality of Zverev's play as early as the third game but took the game to the third seed, particularly in the second and third sets. Zverev always looked to have an extra gear when it mattered, however, and the world No 124 failed to convert any of the five break points he earned. Canada's Shapovalov sealed his spot in the next round by beating American Reilly Opelka 7-6, 4-6, 6-3, 6-4. Italian seventh seed Matteo Berrettini fought off exciting Spanish youngster Carlos Alcaraz and the effects of a heavy tumble to win a fifth-set tiebreaker. Berrettini rolled his right ankle in the second game of the final set but continued on after receiving treatment from the physio. His movement did not appear to be significantly restricted. “I'm good. Luckily it wasn't a big one. I'm used to this,” he said. Berrettini looked to be strolling into the next round as he took the first two sets but the 18-year-old battled back superbly to level the match, only for his more experienced opponent to clinch victory 6-2, 7-6, 4-6, 2-6, 7-6. “He's unbelievable,” Berrettini, 25, said about his opponent. “I think at his age I didn't even have ATP points. “He's impressive and he's proved it playing matches like this. He showed everybody his potential, but luckily today I won. Congratulations to him.” Alcaraz, who is coached by former world No 1 Juan Carlos Ferrero, said he was getting closer to the game's elite. “When I've played against the top players, apart from Rafa [Nadal], I was close,” said Alcaraz, who reached the US Open quarter-finals last year. “I think I have the level to play against the top players. I'm getting close, getting closer every tournament I play.” Next up for Berrettini is Spanish 19th seed Pablo Carreno Busta, who defeated another rising star in American Sebastian Korda, 6-4, 7-5, 6-7, 6-3. French 17th seed Gael Monfils overcame Chile's 16th seed Cristian Garin 7-6, 6-1, 6-3 and will play Serbia's Miomir Kecmanovic, who knocked out Italian 25th seed Lorenzo Sonego 6-4, 6-7, 6-2, 7-5.