Williams missed last year's tournament as she was pregnant, but she has not suffered a defeat at the All England Club since losing to Alize Cornet in the third round in 2014
Seven-time champion Serena Williams has clicked into gear so quickly on her Wimbledon return it is hard to believe she has played only a handful of matches since becoming a mum last September.
While five of the top eight seeds have already tumbled out, the 36-year-old American has stomped past Dutchwoman Arantxa Rus and Bulgarian qualifier Viktoriya Tomova with a minimum of fuss.
It is still too early to label her the favourite though, according to former men's world number one Mats Wilander -- although he admits it will not be long before she assumes that role.
"I'm not surprised how impressive she has looked because she is obviously very easy to train," Wilander, who is presenting Eurosport's Game, Schett and Mats, told Reuters.
"She obviously has an easy time getting back because she has done it so often, coming into a Grand Slam when she hasn't played. I remember in Australia one year she hadn't played and was ranked outside the top 100 and she won."
"I can't go out and say she is favourite to win the tournament -- yet. But every day when she goes on court and you see her across the net from another player, there is no one single player who I would say is favourite to beat her."
"The question is will she have a reaction to playing three or four matches, when she is not returning well or the serve is a bit off. The cumulative effect of playing four or five matches will make her better but more tired."
Williams missed last year's tournament as she was pregnant, but she has not suffered a defeat at the All England Club since losing to Alize Cornet in the third round in 2014.
Wednesday's win over Tomova was her 16th successive victory on the Wimbledon lawns. But her next opponent, France's Kristina Mladenovic, offers a real threat.
Wilander says the key to playing Williams on her favoured grass is trying to drag her into longer rallies.
"When you have that serve and you go for so many returns that she does, you don't have many long rallies," he said.
"It's questionable which type of player can push her into long rallies on this surface. I'm not sure we have many.
"What we don't know though is how she will cope with a couple of tough matches back-to-back.
"But she has already proved in the French Open that she is willing to go out there and suffer, because if she didn't she wouldn't have chosen to come back at the French."
Williams, who has 23 Grand Slam titles, reached the last 16 in Paris in her first Grand Slam tournament since the 2017 Australian, where she won while in the early weeks of pregnancy. But she was forced to pull out of the French before her match against Maria Sharapova with a pectoral injury.