Serena Williams crushed one of the few women to have beaten her in the past 15 months as she began her defence of the WTA Championships in Istanbul with an impressive win on Tuesday.

The world No.1 from the United States took little more than an hour and allowed only four games to Angelique Kerber, who beat her in Cincinnati last year but this time was outplayed almost from the moment she dropped serve in her opening service game.

As usual it was Williams’ superbly produced serve and withering power off the ground which overwhelmed her opponent, and the 6-3 6-1 success suggested she is as far ahead of the field as she has ever been.

Only briefly, when Kerber earned a break back point in the third game, did the German have a glimpse of getting back into it, and Williams soon denied her that with fierce straight drives on the backhand and the forehand.

Williams’ composure was oceanic, and possibly disconcerting.

“Tennis is tranquil for me to get out there,” she said before the match.

“It helps me relax and it makes me calm because I don’t have to worry about all the other stuff going on.”

That apparently referred to business affairs which will presumably take a back seat while she chases the record of grand slam titles during 2014.

Her main rival, Victoria Azarenka, looked care-worn and uncertain by comparison.

She was far from consistent and might easily have lost the first set in a 7-6 (7-4) 6-2 survival against Sara Errani, the sixth seeded Italian.

The world No.2 from Belarus found it hard to force the pace on the slowish surface, lost three of her first four service games, and trailed 2-5.

It confirmed the impression given by her disappointing performances in Beijing and Tokyo that she has not been in the best of health, but she improved after squeezing through the first set tie-break.

“I was a little rusty at the beginning. I think it’s a little bit expected after a break,” she said.