Novak Djokovic lost to world number 109 Taro Daniels in his first match since the Australian Open on Sunday night.
The former world number one was beaten 7-6 (7-3), 4-6, 6-1 in the second round at Indian Wells.
It was his first appearance since a persistent elbow injury ended his hopes of winning the Australian Open in January.
Despite that, he was expected to beat his Japanese opponent, but over the two hour 30 minute match Djokovic made 61 unforced errors.
Djokovic revealed he felt nervous out on court, describing his mindset as ‘very weird’.
‘It felt like the first match I have ever played on the tour, very weird.
‘I just completely lost rhythm, everything, struggled a little bit with the health the last couple of weeks.
‘I was grateful to be out on the court after surgery that quickly but at the same time just didn’t feel good at all. Nerves were there. I made so many unforced errors.
‘I was not even supposed to be here because of the surgery that was only five, six weeks ago. But I recovered very quickly, and I got myself ready.’
Daniels admitted Djokovic wasn’t at his usual levels.
‘He obviously wasn’t in his top form so I was able to take advantage of it,’ he said.
‘And even if I lost the second set, I still had faith I could pull something off in the third. I was able to stay pretty tough, so I’m pretty proud of that.
‘I played the best set of the whole match and that was really good.’