ONE upset was enough during a huge day of National Bank Open semi-finals action, as Reilly Opelka took aim to defeat Stefanos Tsitsipas, before Daniil Medvedev ensured it would not be an all-American final in Toronto with a sweep of John Isner.

Opelka proved just what he is capable of with a massive 6-7(2) 7-6(6) 6-4 victory over Tsitsipas, clinching the biggest win of his career in just over two and a half hours. Whilst the come-from-behind three setter – which included two tiebreakers – was by no means easy, Opelka was hugely impressed by his own performance which included 17 aces for just three double faults, compared to Tsitsipas’ 10 and seven.

“I played great,” Opelka said post-match. “These courts suit my game, it is no coincidence that John Isner is in the other semi-final. “I think we are the two best servers in the tournament, so for us both to be there, it says something about the conditions. ”Stefanos has definitely improved his returning. “Come 5-5 in the first set, a lot of balls started to come back. “He is a thinker and has a high tennis IQ, so it was expected, but that is what separates him from the rest of the pack.”

Opelka also rustled up a handy 46 winners, with 27 coming off his own groundstrokes and proving he has elevated his game from purely service wins. Whilst Tsitsipas won a higher percentage of his first serve points (87 per cent to Opelka’s 77 per cent), he owned a less effective clip which handed Opelka more first service chances and, in turn, more opportunities to fire off his powerful serve and find that slight bit of separation to take out the second set and create his chances in the third to claim victory.

The second match of the day was decided much quicker, as Medvedev dominated proceedings to sweep Isner away in just 55 minutes, 6-2 6-2. Unaccustomed to his service games being rendered so inefficient, Isner failed to adjust to the top seeded Russian’s form as Medvedev ran away with a massive 90 per cent win rate off his first serve – dropping just three points – and backed it up winning seven of his 11 second service points.

“I was playing great today. I think I almost did no unforced errors,” Medvedev said. “I’m really happy with my game at this moment. I always like coming to the US Open Series. I always feel like I’m playing better and better the more the series continues. I’m really happy that I’m still in the Toronto tournament, that’s the main [thing].”

“I had to take this opportunity, just try to break as many times as I can, stay focused and I managed to do it,” Medvedev said. “I’m really happy with the win today.”

While Isner was by no means inefficient on his first serve – although lower than his usual service rating – winning 61 per cent of points, it was on his second serve where the wheels well and truly fell off and Medvedev capitalised, as the American won just two of 12 second serve points to all but hand Medvedev the commanding victory.

NATIONAL BANK OPEN SEMI-FINALS RESULTS: 

[1] Daniil Medvedev (RUS) defeated John Isner (USA) 6-2 6-2
Reilly Opelka (USA) defeated [3] Stefanos Tsitsipas (GRE) 6-7 7-6 6-4

Picture credit: Vaughn Ridley/Getty Images