Watch: ATP stars identify famous Austrians, Dimitrov calls Dominic Thiem a 'cutie' and Zverev jokes 2020 USO trophy belongs to him

The 2021 Erste Bank Open commenced in Vienna this week, and it is no coincidence that the tournament was scheduled to begin around Austrian National Day, which is celebrated every year on October 26.

Dominic Thiem is not competing in the tournament due to a wrist injury, but the organizers made the most of having some of the best ATP players around by getting them to participate in social media shenanigans to mark the occasion.

Matteo Berrettini, Grigor Dimitrov, Hubert Hurkacz, Felix Auger-Aliassime, Casper Ruud, Alexander Zverev and Carlos Alcaraz were all quizzed about Austria's Finest.

In a two-part video released on Twitter, the tournament shared the players' reactions after they were asked to recognize famous Austrians from their pictures. The list included legendary music composer Mozart, actor Arnold Schwarzenegger, singer Conchita Wurst and former US Open champion Dominic Thiem.

The picture of Thiem holding his 2020 US Open trophy aloft brought out some fun reactions from the players. Referring to his loss to Thiem in the US Open final after being two sets up, Alexander Zverev jokingly stated that the trophy belonged to him.

"I should have been with that trophy, not him," Zverev pointed out after breaking into a big laugh. "Nah, I'm kidding, it's Dominic, of course!"

Grigor Dimitrov, meanwhile, had a big smile on his face as he pointed out how hard it is to play aggressively against a "cutie" like Thiem.

"Awwh, look at that cutie. That's Dominic," Dimitrov said. "Picture if I didn't guess that one."

Unvaccinated Dominic Thiem misses out on watching Erste Bank Open from the stands

Dominic Thiem at the 2021 French Open - Day One

The vaccination status of tennis players has become a hotly debated issue in the run-up to the 2022 Australian Open. There is still plenty of uncertainty over whether unvaccinated players will be allowed to participate in the Grand Slam due to strict measures being taken by the Victorian state government.

Meanwhile, Thiem, who has yet to be inoculated, was unable to attend the Erste Bank Open due to strict rules from the organizers stating that all attendees must have received the vaccine. As expected, no exceptions were made for the 28-year-old.

Thiem has been waiting for a specific vaccine (Novavax) upon suggestions from his doctor, but indicated that he would be open to taking alternatives if the vaccine was not available by November.

"I haven’t been vaccinated yet. I want to wait for the Novavax vaccine because I heard from my doctor that it should be really good," Thiem said. "If it works out by the end of November, I’ll have it vaccinated. If not, I’ll get something else vaccinated."