Defending champion Serena Williams needed just 45 minutes of playing time to advance to the fourth round of the Australian Open. The world number one defeated Russian teenager Daria Kasatkina 6-1, 6-1.Four-time champion Roger Federer also reached the last-16, beating Grigor Dimitrov 6-4, 3-6, 6-1, 6-4. It was the Swiss third seed’s 300th Grand Slam match win.