South Korean qualifier Chung Hyeon upset sixth-seeded Borna Coric, a finalist last year, in a 6-3 7-5 victory in the first round of the Chennai Open on Monday.
Chung continued his fine form from the qualifying and proved too strong for the highly-rated Croat in a baseline slugfest at the Nungambakkam stadium.
The South Korean capitalised on Coric’s sluggish play to win the first set, as the world No.48 struggled to find his range.
The second set was more of a contest as the two players traded big forehands and backhands.
Chung held for 6-5 with a few powerful shots, before Coric surrendered his serve meekly by making unforced errors in the next game, with the match ending when he sent a backhand wide.
Chung now faces Israel’s Dudi Sela, who kept Damir Dzumhur of Bosnia on the run with pinpoint ground strokes to post a comfortable 6-2 6-2 win
In other matches, Daniil Medvedev beat Thiago Monteiro of Brazil 6-3 6-3 and Belgian Steve Darcis quelled the challenge of Croatian qualifier Nikola Mektic 6-2 6-3 to face third-seeded Spaniard Albert Ramos-Vinolas in the second round.
The 99th-ranked Medvedev’s booming serves and powerful groundstrokes left little doubt about the result between two players making their first appearances at the event.
Riding on his serve, the 20-year-old Russian hit eight aces – on top of several unreturnable ones- with the Brazilian left-hander only briefly rallying in the second set.
Medvedev next plays either eighth-seeded Yen-Hsun Lu or Radu Albot.
Top-seed Marin Cilic had a first-round bye.