The Serb, trying to become the first man in the professional era to win the title in four consecutive years, looked in ominously good form as he took his place in the last 16 without dropping a set.
"I feel better on the court as the tournament is progressing," the second seed told reporters.
"I played in different conditions in the three matches. The roof was closed tonight and temperature dropped at least 10 degrees and you could feel that. It affected the play. It was much slower.
"I needed to have very fast footwork and a precise first service, as high a percentage as possible, using every opportunity to take control over the rally. I've done really well."
Djokovic cruised through the opening two sets and looked set to wrap it up when he served for the match at 5-4, only to be broken.
The 26-year-old made no mistake second time round to set up a meeting with Italy's Fabio Fognini.
"At 4-2, he asked for the crowd support and he got it," Djokovic said.
"They lifted him a little bit and he started hitting the ball really well.
"Things got tense towards the end of the match and I made some double-faults.
"This is what happens. I could have easily got into a tiebreak and then it's very even, very unpredictable who is going to win the third.
"I didn't want to drop the third set, obviously, so I was very focused to get the job done in straight sets."
Djokovic and Fognini know each other from their junior days and the second seed said he would not take anything for granted.
"He's a claycourt specialist, that's where he made his best results," Djokovic said of the Italian.
"But lately he's been performing really well on hard courts. Today he beat Sam Querrey, who is a hard-court specialist, big serve, in form.
"I don't take anything easy. I try to do as best as possible."
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