●Williams’s average serve speed has gone from 90 mph to 98 mph, while her average top serve speed has increased from about 115 mph to 120 mph, meaning she is going for bigger serves and more easy points.

●Williams’s combined rally length when serving and receiving has fallen from 4.5 shots to four shots, indicating that she is ending rallies more quickly.

●Williams is spending 10 fewer minutes per match on court compared to eight years ago, dropping from about 90 minutes to 80 minutes on average. This includes both WTA and Grand Slam contests. This year she is averaging 77 minutes.

“I just feel like I try to be as efficient as I can out on the court,” Williams told reporters . “That’s not always possible. But I just feel like my game has matured a lot overall, and mentally sometimes I definitely do put a little more pressure on myself than I did a long time ago.”

The statistics also show that she is covering more distance in her matches, meaning she is expending more energy by running more. Her total number of winners and unforced errors have also ticked up, with the ratio of errors increasing.

Mouratoglou says this could be because he has also tried to instill a plan B when Williams’s power game is off. “We’ve worked on being able to hit more shots if necessary,” he said.
Some of her opponents have noticed  the change too,“Now she’s more aggressive,” said No. 7 seed Roberta Vinci, 33, who slammed the door on Williams’s Grand Slam bid in last year’s U.S. Open semifinals. “The point is more quick than 10 years ago.”

Second-seeded Angelique Kerber, who defeated Williams in the Australian Open final but finished runner-up to the American at Wimbledon, did not hesitate when asked who was the most efficient power player in women’s tennis.

culled from Washington Post