Alexander Zverev said his game was on the up after a poor start to the year as he came through three tight sets to beat 98th-ranked Egor Gerasimov at the Australian Open on Thursday.
The German seventh seed has been practising up to seven hours a day after a dismal ATP Cup and the hard work paid off as he safely reached the third round.
"Definitely much better than the ATP Cup. Now in the third round, I'm very happy about that," said the 22-year-old, who beat Italy's Marco Cecchinato in round one.
The 6ft 6ins (198cm) Zverev sent down so many double faults at the ATP Cup that Belinda Bencic suggested he donate to Australia's bushfires appeal for each one.
But his serve, a key focus of his extended practices, was a weapon once again on Thursday as he fired nine aces against no double faults, with a first-serve percentage of 78 percent.
"Sometimes it's difficult, sometimes it's easy," Zverev said when asked what it was like trying to rediscover form.
"The last week or so when we were practising, we were spending six or seven hours a day on court trying all kinds of things to find my game."
Zverev will next play Fernando Verdasco or Nikoloz Basilashvili as he attempts to match his best Australian Open result after reaching the round of 16 last year.