It was another snag in the return for the 30-year-old Djokovic who admitted he was out of sorts while playing in just his second event of 2018.
He is making a cautious return to the ATP Tour after stopping his 2017 season following Wimbledon, due to a right elbow injury.
"For me it felt like first match I ever played on the tour. Very weird," Djokovic said. "I mean, I just completely lost rhythm, everything. Just struggled also a little bit with the health the last couple of weeks."
Djokovic scrambled to win the second set but looked rusty on stadium court, making 62 unforced errors compared to 29 for Daniel.
Djokovic had four aces but overall he served poorly making four double faults and winning just 65 percent of his first-serve points.
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