Rafael Nadal accepts he will have to perform better than he did against John Isner if he is to overcome "dangerous" opponent Denis Shapovalov at the Internazionali d'Italia.
The world number four's bid for an 11th title in Rome got off to a strong start on Wednesday as he saw off big-serving Isner 6-3, 6-1 in a time of 76 minutes.
Isner twice missed the chance to break Nadal in the seventh game of the opening set and the Spaniard took control from that point on in the second-round match.
Nadal, who has won this tournament in three of the past four years, identified that hold of serve as a key point in the contest.
"The beginning of the match was not good for me," he said in his on-court interview. "He had some chances on the return and had two break points.
"He had two not difficult balls so I was in his hands at that moment. I was lucky that he missed those shots and then I was able to break.
"Then the match changed, of course. With the first set on the board, and having the break in the first game of the second set, everything changed."
Nadal will now face Shapovalov in a repeat of last year's last-16 encounter, which the record 21-time grand slam winner edged in three sets after saving two macth points en route to the title.
And Nadal, who was beaten by Carlos Alcaraz on clay in last week's Madrid Open quarter-final, is not expecting an easy task this time around.
"Last year was a joke, the match that I saved here against him," said Nadal of his next opponent. "I was super lucky. I know how dangerous he is, I need to play well.
"I need to play better than today, but after a while without being on court it is another victory and I have the chance again to play against one of the best players in the world.
"I need to build things again after a tough stoppage and that's what I am trying now. I just need to stay with the right attitude, and let's see if I am able to make that happen."
Alexander Zverev also booked his place in the last 16 on Wednesday thanks to a 7-6 (8-6), 6-3 victory over Sebastian Baez.
Last week's Madrid Open runner-up was given a tough time of things by in-form Baez who recovered from 6-2 down to 6-6 in the first-set tiebreak, but ultimately came through unscathed to stay on course for his first title of the year.
"It could have gone either way. I am happy to advance. It is never easy to come to Rome from Madrid," Zverev said.
