Serena, Kyrgios advance

Serena toils to scrappy win in opener

Serena Williams reacts after winning a point during her first round match against Amra Sadikovic of Switzerland.

 Defending champion Serena Williams stuttered to a low-key and error-strewn 6-2, 6-4 first-round victory over Swiss qualifier Amra Sadikovic.

Looking ill-at-ease, as though her quest for an elusive 22nd Grand Slam title was weighing heavily on her shoulders, Williams struggled with her serve and sprayed balls wide on both sides of the court. She served three double faults in the fifth game of the first set.

It was Williams's first match since she lost the French Open final to Garbine Muguruza this month and the American should have had few problems against Macedonian-born Sadikovic, ranked 148th in the world and with little main tour experience.

By turns urging herself on and telling herself off, Williams eventually secured match point when her opponent just missed a lob and sealed victory after challenging a wrong call when her shot landed on the far baseline.

 Kyrgios overcomes gritty Czech veteran Stepanek

Nick Kyrgios serves during his first round match.

 Australian 15th seed Nick Kyrgios overcame the gritty challenge of Radek Stepanek, winning 6-4, 6-3, 6-7(9), 6-1, foiling the Czech player's bid to become the oldest man to win a Grand Slam singles match in almost 25 years.

After the players exchanged breaks of serve early on -- the Australian playing a lax seventh game to concede his -- Kyrgios made the decisive break of the first set in the tenth game.

Kyrgios took the second on a single break and had the chance to wrap things up in straight sets when he served for the match at 5-4.

But the Czech, at 37 Kyrgios's senior by 16 years, broke back and took the third set in a marathon tie-break 11-9, luring Kyrgios to the net with one of many drop shot before passing him with a cross-court forehand.

That burst of energy seemed to tire the Czech, and Kyrgios -- who next plays Germany's unseeded Dustin Brown -- stormed through the fourth set with two further breaks of serve to wrap up victory in two hours and 26 minutes.