Austrian star Dominic Thiem emotionally bid farewell to tennis fans during a show match in Vienna on Sunday, two days before what could be his last professional match. In an exhibition match that brought back memories of his Grand Slam success, Thiem took the set against long time competitor Alexander Zverev 6-3. Thiem and Zverev faced off in the 2020 US Open final in New York, where Thiem made an incredible comeback from two sets down to claim the biggest success of his tennis career, winning his lone grand slam. The event in Vienna drew a crowd of 5,000 spectators and featured tennis legend …