Both world No 136 Nagal and world No 124 Kovalik came into the main draw through qualifying rounds and the Slovak prevailed 3-6, 6-1, 6-3 in a contest that lasted for two hours and 13 minutes.
French Open 2019: Serena Williams survives first-round scare; Rafael Nadal, Novak Djokovic post straight-sets wins
Serena Williams survived a first-round scare at the French Open while Rafael Nadal and Novak Djokovic both eased through to the second round.
Sofia Open: Qualifier Mirza Basic shocks Stan Wawrinka to reach maiden final, set to meet Marius Copil
Mirza Basic bludgeoned his way to a shock 7-6(6), 6-4 victory over top seed Stan Wawrinka to set up an intriguing title clash against big-serving Marius Copil.
Stan Wawrinka outclassed Viktor Troicki 6-1, 7-6(3) to book his place in the semi-finals of Sofia Open and suggest that his recovery from a knee injury is well under way.
On Monday, as Monfils faded away in the third set, Wawrinka powered on, punching those monstrous groundstrokes to underline an impressive performance. It was the kind of performance that showed that Wawrinka was dangerous again.
Fernando Verdasco eliminated the in-form Alexander Zverev 6-4, 3-6, 6-4, 6-2 in a first round match that was suspended overnight after a long debate between both players and the umpire.
World number one Andy Murray faces Andrey Kuznetsov, the world number 85, in his opening round. Third seed Stan Wawrinka, the 2015 winner and reigning US Open champion, starts against Jozef Kovalik.
The semi-final lineup at Chennai Open on Saturday promises some great action to bring us closer to the end of the opening week of tennis this season.
Daniil Medvedev earned his maiden entry into the singles semifinals of an ATP World Tour event when he ended the dream run of Slovakian qualifier Jozef Kovalik with a commanding win in the Chennai Open quarterfinals
Terming the surprise loss against little known Jozef Kovalik as "small stumble", Marin Cilic says he is ready to challenge the 'Big Four' in the 2017 season since he has taken a "huge step forward" with new coach Jonas Bjorkman on the motivational front.
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.
Davis Cup: Nick Kyrgios, Bernard Tomic complete straight set wins to give Australia 2-0 lead over Slovakia
Nick Kyrgios and Bernard Tomic claimed straight set victories to give Australia a commanding 2-0 lead over Slovakia in the Davis Cup World Group playoff.