Miami: The 30-year-old, a finalist at Flushing Meadows in 2014, withdrew from the Western & Southern Open hard court event after his first positive test, casting doubts over his participation in the Grand Slam tournament which starts on Monday. “I am happy to announce that I tested negative for COVID-19. Having said that, I (together with my team) have decided to skip the US Open,” the former World No.4 said on his website.