Victoria Azarenka returned to action with a 6-2 6-3 victory over Romina Oprandi in the second round of the Qatar Open.
Fresh from her second successive Australian Open title, the Belarusian did not need to be at her best to despatch the Swiss in an hour and 12 minutes.
Azarenka was pressurized on her serve, dropping her first service game, although it proved to be Oprandi's only break of the match as the world No 1 saved a further six break points.
Oprandi was broken three times in the first set and Azarenka quickly established a 3-0 lead in the second and never looked back.
"It was a little bit of a slow start, and I had to adjust," said the defending champion. "I couldn't go for my shots, and I had to be a bit more patient.
"She's tricky and plays so many different balls that you don't know what to expect. I had to focus more and move my feet more."
Fourth seed Agnieszka Radwanska enjoyed a straightforward 6-3 6-2 victory against Anastasia Rodionova of Australia, while sister Ursula claimed a surprise win against 15th-ranked Roberta Vinci 6-2 5-7 6-0.
There were also wins for 11th seed Nadia Petrova over Su-Wei Hsieh and 13th ranked Ana Ivanovic, who came through against Simona Halep.
Sixth seed Sara Errani wasted little time in beating Timea Babos of Hungary 6-4 6-0, while 10th seed Caroline Wozniacki was also successful against Sorana Cirstea (7-6 6-0)
But there was a shock when in-form 16th seed Sloane Stephens was ousted 4-6 7-6 7-6 by Czech Klara Zakopolova.
She was joined by compatriot Petra Kvitova, the seventh seed strolling into the third round after Russian Ekatarina Makarova retired after dropping the first set 6-4.