Stefanos Tsitsipas survived a minor scare in the first round of the Vienna Open before ultimately going on to beat Grigor Dimitrov in straight sets.

It was neck-and-neck for much of the first set, with neither player losing serve, but Dimitrov appeared to have the upper hand when he got to 6-3 in the tiebreak.

Tsitsipas recovered emphatically, however, the top seed reeling off five successive points to win the set and he went on to book his spot in the second round thanks to a 7-6 (8-6) 6-4 victory. He will face Frances Tiafoe next.

"Grigor is a tough competitor and the level of tennis was really high today. We both competed at our highest [level]," Tsitsipas said afterwards.

"That was great tennis that was being played during the entire match and I got really close to my [best] offence and showed incredible attitude [in] the last game, which was the one that was the most crucial of the match."

Alexander Zverev, seeded second, was also made to work in his first-round clash with Filip Krajinovic.

While he blew the Serbian away in the first set, he found himself 5-2 down in the second as Krajinovic looked set to level the match, but Zverev scrapped his way back and then served to love to win 6-2 7-5. Alex de Minaur awaits the German.

Casper Ruud and Felix Auger-Aliassime, seeded fourth and sixth respectively, were two other high-ranking players who also secured progression, boosting their ATP Finals qualification hopes.

Ruud was pushed hard by Lloyd Harris but eventually outfought the South African in his 7-5 7-6 (7-2) win, while Auger-Alisassime made fairly light work of Ricardas Berankis 6-3 6-2.

Indian Wells champion Cameron Norrie, who is also in with a shot of reaching the ATP Finals, beat Marton Fucsovics 7-6 (7-4) 6-1 to set up a meeting with Auger-Aliassime – the British number one is 11th in the FedEx ATP Race to Turin rankings, one above his next opponent.

At the St Petersburg Open, fifth-seed Taylor Fritz was the highest-ranked player in action and he needed a little over an hour to beat Emil Ruusuvuori 6-1 6-4.

Pablo Andujar defeated Federico Delbonis to set up a meeting with second seed Denis Shapovalov, while Ilya Ivashka beat Laslo Djere for the right to tussle with tournament favourite Andrey Rublev next.