Novak Djokovic admits he did not feel comfortable on the court after scraping past qualifier Bjorn Fratangelo at the BNP Paribas Open on Sunday.
Djokovic went down in the first set against his American opponent but recovered to seal a 2-6 6-1 6-2 victory and a place in the last 16 in Indian Wells.
The world number one, who is 17-1 in 2016, was coming off a marathon win over Mikhail Kukushkin in Serbia's 3-2 victory over Kazakhstan in the Davis Cup.
That match took its toll on Djokovic but he was still full of praise for Fratangelo, who sits 148 places below the Serbian in the ATP rankings.
"All credit to Bjorn on playing a great match, but I wasn't feeling comfortable at all on the court," he said after the match.
"I was just trying to find a way, trying to hang in there and make it through."
"He deserved every point he got. He played a great match, especially in the first set."
Djokovic will face Philipp Kohlschreiber in the third round after the German eased past Denis Kudla 6-0 6-1 earlier in the day.