(Reuters) - Australian Open champion Angelique Kerber rebounded from early exits at her last two tournaments with a 6-1 6-1 second-round victory over Barbora Strycova at the Miami Open on Friday.
Kerber, who beat world number one Serena Williams to claim her maiden grand slam title in Melbourne, improved her record against the Czech to 4-0 without dropping a set.
Kerber fell at her first hurdle in Doha last month and again last week in Indian Wells, an exit that gave her plenty of time to prepare for Miami.
"I worked very hard before Miami, because I had a lot of time after Indian Wells and I think the hard work pays off again," Kerber told reporters. "I'm also a little bit more relaxed and healthy.
"At the end of such a great success it's always good to celebrate a little bit and of course no one can ever take it away from me.
"But now it's time to get on court and work hard again and do the same things that made me strong before Australia, getting ready for my next matches and tournaments."
In other matches on Friday, 10th seed Venus Williams was beaten 6-0 6-7(5) 6-2 by Elena Vesnina. The Russian qualifier, who squandered a match point in the second set, expressed surprise with the result.
"I honestly was a little bit shocked after the first set, thinking, 'Ok, what's going on?'" Vesnina said.
"Even when I was up 5-3 (in the second set), I felt Venus was playing better and better and she raised her level up."
Fourth seed Garbine Muguruza of Spain beat Slovakian Dominica Cibulkova 6-7(3) 6-3 7-5 in a match that lasted nearly three hours.
World number 54 Cibulkova seemed poised for an upset when she led 3-0 in the final set, but was broken in the fifth game and again in the penultimate game.
Seventh seed Belinda Bencic of Switzerland (back) and 18th-seeded Serbian Jelena Jankovic (shoulder) both retired from their matches.
Sixth-seeded Spaniard Carla Suarez Navarro also bowed out, losing 6-4 6-2 to American Coco Vandeweghe, while 14th seed Sara Errani of Italy fell 6-1 6-3 to Japanese wild card Naomi Osaka.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Larry Fine/Peter Rutherford)