Old rival Martina Hingis says Serena Williams is playing more strategically than when the two had their battles a decade ago.
Hingis, 33, said she wasn't surprised to see Williams still at No. 1 12 years after first reaching the top spot.
"Well, she is playing smart," Hingis told reporters in Miami, where she won the doubles with Sabine Lisicki.
“It's a combination of all those years on tour and the influence of coach Patrick Mouratoglou,” added Hingis, who has worked for Mouratoglou's academy and took part in the 2012 offseason training camp which Williams also attended.
"You know, she uses her experience. And also, in the last two years, she's done pretty well, I think, with Patrick Mouratoglou. He's helped her with a couple of things to play smarter. Obviously before she was already winning Grand Slams, and now he helps her to get back to the top again."
Williams also says she is doing more scouting and adjusting her game plans.
"I don't go in with the same strategy," Serena said. "I think that's what I have been doing a little more different, working with Patrick in particular. But still, my route is just to play my game, my strategy.
"I don't get too overly involved into what my opponent is going to do, but know their weaknesses a little bit better."