Kohlschreiber, 35, stunned the top seed and five-times former champion 6-4 6-4 in Indian Wells, leaving the Serb to conclude it had just been "one of those days".
"To be honest, I don't enjoy losing, nobody does, but especially in a tournament like this, a tournament where I have had plenty of success in the past," Djokovic said.
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I thought I was in good form. I was practicing well. But it just happens, one of those days. You just have to deal with it, move on, turn the next page.
The tournament in Indian Wells was Djokovic's first since winning his seventh Australian Open title in January and the 31-year-old said he had already put the defeat behind him and turned his thoughts to next week's Miami Open.
"I had to get over it in an hour, because I played doubles," Djokovic added. "I must admit I was thinking about it... but it's part of our world, and we just have to bounce back very quickly.
"Miami is the next tournament singles-wise for me. I'm not at my highest level, I know that... but hopefully I'll be able to peak in Miami."
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