Korean qualifier Hyeon Chung produced the first upset of the ATP Chennai Open by ousting last year's finalist Borna Coric with a straight-set win in the opening round of the $505730 hard court event in Chennai on Monday.
Coric, the World No 48, struggled with his first serve and forehand today while Chung was unrelenting in his 6-3, 7-5 win over the Croat.
Coric, who struggled with his knee last season, said it was not an issue.
"It was not due to my knee. My serve was off today and I did not play well. I am not surprised with the way he (Chung) played. I knew he was a good player," Coric said after a disappointing start to the new season.
Coric struggled in the entire two hours and one minute contest as he was broken in the very first game of the match. He held on to his second service game but a double fault saw him yield the advantage back to Chung in the fifth game. Down 3-5, he double faulted again to be locked in a battle of deuces.
An unforced error by him gave the opening set to Chung.
The second set went with serve till 4-4. Coric surged into the lead, breaking Chung in the ninth game. But Chung broke him in his next two games to wrap up the match.
Chung will next challenge Israel's Dudi Sela, who convincingly defeated Bosnia and Herzegovina's Damir Dzhumhur 6-2, 6-2.
Another qualifier to make the second round was Slovakia's Jozef Kovalik, who sent packing Portugal's Elias Gastao as he rallied to eke out a 6-7(5), 6-4, 6-2 win in two hours and 20 minutes.
He next books a match with top seed and tournament favourite Marin Cilic, who had got a bye in his opening round.
Russia's Daniil Medvedev also made it to the next round with a 6-3, 6-3 win over Brazilian Thiago Monteiro. Medvedev had rushed to a 4-1 lead in the opening set but allowed Monteiro to trouble him by not containing his unforced errors.
Meanwhile, Belgium's Steve Darcis subdued Croatian qualifier Nikola Mektic 6-2, 6-3 to set up a second round contest with third seed and world number 27 Albert Ramos-Vinolas from Spain.