"For me it felt like first match I ever played on the tour", Djokovic said after his defeat, as quoted by ATP's official website.
World No.3 Marin Cilic of Croatia on Sunday defeated Hungary's Marton Fucsovics 7-5, 6-3 to set up a third-round clash with Germany's Philipp Kohlschreiber, who beat Tim Smyczek of the United States 1-6, 6-4, 6-4.
JAPANESE qualifier Taro Daniel sent five-time tournament champion Novak Djokovic tumbling out of the Indian Wells Masters with a hard-fought 7-6 (7-3) 4-6 6-1 victory on Monday (AEST).
Federer and Delbonis resumed their match from Saturday which was called off by rain with Federer up by one set. Djokovic who had been out of action for nearly two months after his defeat against Korean Chung at the Australian Open had taken the second half of 2017 off to heal from an elbow injury. But at the same time, just didn't feel good at all.
"But he's strong enough to deal with that, and I love him and I want to see him in the top positions very soon".
"I just completely lost rhythm, everything", said Djokovic.More news: Ivan Rakitic: 'I'd welcome Neymar return to Barcelona'
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"It is still early stages for Novak coming back and the first one after surgery". Last month, Djokovic underwent another surgery on the same elbow, with hopes of returning to his best closer to the European claycourt and grasscourt seasons.
"Unfortunately I have to pull out", Nishikori said.
"And even though you don't have pain, you're still thinking about it, because it's been something that I have been feeling and dragging for over two years".
The defeat was just the fifth time in the past decade former world number one Djokovic has lost against a player outside the top 100 players in the world.
Argentina's Juan Martin Del Potro (6) defeated Australia's Alex De Minaur 6-2, 6-1 to set up a third-round match with Spain's David Ferrer (29), who beat American Tim Smyczek 6-2, 7-6 (3).
South African seventh seed Kevin Anderson also prevailed in his second round match, 7-5 6-4 over Russian Evgeny Donskoy.