Novak Djokovic is satisfied with his progress at the French Open, but has warned he has "a couple more gears" after coming through a much-delayed fourth-round meeting with Roberto Bautista Agut.
Persistent rain prevented the world number one from playing on Monday, while further showers limited Djokovic and Bautista Agut to two sets and five games of action 24 hours later.
Djokovic eventually secured a last-eight meeting with Tomas Berdych on Wednesday, beating Bautista Agut 3-6 6-4 6-1 7-5.
The world number one, who is seeking his first title at Roland Garros, said: "It's the same for you and your opponent. But it was a great mental test for all of us, really, yesterday.
"I'm, in a way, glad to have a match like this, because it's a challenge that you need to overcome mentally mostly.
"I'm in the quarter-finals, and I dropped one set. So, you know, things are going the right way.
"Of course I know that I can play better and I have a couple more gears. That excites me, actually, motivates me to work and get myself in that maximum speed hopefully for the next match and see where it takes me."
Djokovic and Bautista Agut were able to play for two hours amid a series of delays on Tuesday.
"Yesterday the match was interrupted three times, and of course it wasn't easy coming into the facilities here at 9am and leaving at 7:30 or 8pm, but it's not the first and probably not the last time I'm going to have to face these particular circumstances," said the Serbian.
"Not only for us players but it was difficult for all the crowds that were coming in and paying tickets to watch the matches. Then they watch maybe an hour and then they go home, and two days ago, [there were] no matches at all.
"Weather conditions are something you can't really affect if you don't have special abilities. Other than that, you have to wait and pray for good weather, and that's what we did."
In an on-court interview after beating Bautista Agut, Djokovic raised a smile by wearing the rain hat of his interviewer, former player Fabrice Santoro.
"He was obviously well prepared in case it rains," said Djokovic. "We just had a little joke about it. A joke cannot hurt anybody, and it's good to bring a little bit of positive energy in these grey days."