Alexander Zverev admits he's growing weary of the question—and is convinced he has the answer.

The fourth-ranked Zverev has reached a Grand Slam fourth round just once in 10 majors, but remains "very, very sure" his major breakthrough is coming.

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"Obviously I’m waiting for the breakthrough," Zverev told the media in Beijing. "Not waiting; I’m doing a lot of stuff for it. I’m practicing, working hard. I’m sure it will come. I’m very, very sure about it.

"As I said, the only bad match I played at a Grand Slam was at the US Open. I’m always very honest with you guys. I always say when I played a bad match and when I felt like the opponent played better.

"As I said, all the other slams I just felt like my opponent was better than me on that day."

The 20-year-old German has won five titles this season, including Masters championships in Rome, where he topped former No. 1 Novak Djokovic, 6-4, 6-3, in the final and Montreal, where he defeated former No. 1 Roger Federer, 6-3, 6-4, in the title match.

Zverev posted a career-best fourth-round result at Wimbledon where he fell to 2016 finalist Milos Raonic in five sets. Borna Coric surprised Zverev in the US Open second round that he regards as his only subpar performance in a major this season.

"I have answered this question a lot of times," Zverev said of his Grand Slam results. "As I said, this year I didn’t lose bad Grand Slam matches, apart from the US Open. US Open I think was bad for me. I think I played bad.

"Apart from that, you know, I lost to Rafa five sets in Australia. I lost to Milos five sets at Wimbledon, who was the finalist the previous year. You know, even in Roland Garros I felt like Fernando Verdasco played a good match against me, and especially it was not easy because I’d just won my first Masters in Rome. Maybe people were expecting a little bit too much from me, but that was something that I was never through, so I had to learn as well."

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