Day 5 at the US OpenUpdated 2217 GMT (0617 HKT) September 2, 2016 Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds. Photos: US Open continuesRoberta Vinci moved a step closer to another final at the US Open by beating Carina Witthoeft. Hide Caption 1 of 8 Photos: US Open continuesVinci, who stunned Serena Williams last year, won 6-0 5-7 6-3 to reach round four. Hide Caption 2 of 8 Photos: US Open continuesComeback of the day went to Madison Keys. She trailed 5-1 in the third before defeating Naomi Osaka 7-5 4-6 7-6 (7-3). Hide Caption 3 of 8 Photos: US Open continuesTwo-time US Open finalist Caroline Wozniacki -- who meets Keys next -- followed up her upset win over Svetlana Kuznetsova by defeating Monica Niculescu 6-3 6-1. Hide Caption 4 of 8 Photos: US Open continuesNovak Djokovic got more good luck when his opponent, Mikhail Youzhny, retired trailing 4-2 in the first set. Hide Caption 5 of 8 Photos: US Open continuesDjokovic -- the world No. 1 -- didn't have to play in the second round because of an injury to opponent Jiri Vesely. Hide Caption 6 of 8 Photos: US Open continuesJack Sock took out 2014 winner Marin Cilic 6-4 6-3 6-3, two weeks after Cilic won the prestigious Cincinnati Masters. Hide Caption 7 of 8 Photos: US Open continuesJo-Wilfried Tsonga moved on by winning against an ailing Kevin Anderson 6-3 6-4 7-6 (7-4). Anderson upset Andy Murray last year in New York. Hide Caption 8 of 8Last year's finalist Roberta Vinci and defending men's champion Novak Djokovic were among those who advanced. More from Sport - TennisSanchez-Casal Academy: The making of Andy MurrayMaria Sharapova: Russian wins on return from 15-month doping banMaria Sharapova's comeback leaves women's Tour dividedSerena Williams slams Ilie Nastase over 'racist' commentsCan Serena Williams return to the top of tennis after giving birth?