Federer played in the Hopman Cup and Australian Open in January 2017. His withdrawal from most of the injury affected 2016 season lead his ranking slip to No. 17 at the start of Australian Open, his lowest in over fifteen years. At the Australian Open, he beat top-10 players Tomáš Berdych and Kei Nishikori on his way to semifinals, making Federer the oldest man to compete in a grand slam semi-final since Jimmy Connors in 1991. In the semi-finals, he defeated Stanislas Wawrinka in five sets, making him the oldest player to compete in a Grand Slam final since Ken Rosewall in 1974. Coming back from a break down in the fifth set, Federer defeated Rafael Nadal to win the Australian Open, which also marked Federer's 100th match at the Australian Open; it was the first time Federer had won a match against Nadal in a Grand Slam event since the 2007 Wimbledon final, and also marked Federer's first ever Grand Slam victory over Nadal outside the grass courts of Wimbledon. With this victory, he re-entered the top ten.