Dominic Thiem's latest bid for Grand Slam glory came to an abrupt end at the U.S. Open on Tuesday, when he fell to unseeded Thomas Fabbiano 6-4 3-6 6-3 6-2 in a shock first-round exit, the biggest upset of the men's competition so far. The fourth-seeded Austrian's blistering serve yielded 14 aces but it was not enough to overcome the 30-year-old Fabbiano, whose fearsome forehand helped him save nine out of the 10 break points he faced. The 25-year-old Thiem did himself no favours, committing 48 unforced errors during the match on Arthur Ashe Stadium, 28 more than his Italian opponent. "I beat a top-10 guy in Wimbledon and another one here," said Fabbiano, who upset world number eight Stefanos Tsitsipas in their first-round meeting at the All England Club in July. "I'm starting to like to play these big matches and my game is coming better and better." For Thiem, who toppled titan Roger Federer earlier this year in the final at Indian Wells, the loss marks the latest frustration in his bid to claim a Grand Slam title. Thiem was beaten by the King of Clay, Rafa Nadal in the 2018 and 2019 French Open finals, as well as in their quarter-final match at last year's U.S. Open.