Maria Sharapova won on her return to action after a 15-month doping ban as she beat Roberta Vinci in the first round of the Stuttgart Open.
Serena Williams, the most successful female player of the Open era, is pregnant - just 12 weeks after winning her record 23rd Grand Slam.
World number two Novak Djokovic won on his return to the tour as he beat France's Gilles Simon in his opening match of the Monte Carlo Masters.
Andy Murray saved seven match points in a 31-minute second-set tie-break before beating Philipp Kohlschreiber in the Dubai Championships quarter-finals.
Six-time champion Serena Williams outplayed Britain's Johanna Konta to reach the Australian Open semi-finals.
Britain's world number one Andy Murray will play Ukraine's Ilya Marchenko in the Australian Open first round.