Australia's John Millman has scored a hard-fought three-set victory over Russia's Evgeny Donskoy to advance to the second round of the Chennai Open.
The 26-year-old from Brisbane was forced to come from behind on Monday to score an impressive 6-7 (5-7) 6-4 7-6 (8-6) win.
He will meet No.4 seed Roberto Bautista Agut from Spain for a spot in the quarter-finals.
Novak Djokovic opened his season with a 6-2 6-2 first-round win over German qualifier Dustin Brown.
The top-ranked Serb avoided the post-season exhibitions last month after an exhausting 2015 season in which he won three majors and reached the final in the other.
The Qatar Open was the only tournament out of 16 that Djokovic played last year in which he failed to reach the final, losing in the quarters.
Last year, Djokovic won a career-best 11 titles and finished with an 82-6 record.
"Obviously, you never know how you're going to start from the blocks," Djokovic said. "I think I used the off-season very well to train to get my body in the right shape, and I think it was a very good start."
Spaniard Daniel Munoz De La Nava posted the first upset of the tournament, defeating fifth-seeded countryman Feliciano Lopez 3-6 7-6 (7-4) 7-5.
Seventh-seeded Jeremy Chardy of France beat Qatari wildcard Mubarak Shannan Zayid 6-1 6-1.
