Wimbledon 2018: Serena Williams, Roger Federer & Venus Williams in action on Friday

Serena Williams (right) has won seven Wimbledon titles

Serena Williams has already shown glimpses of her best form at Wimbledon and will be hoping to extend her run with victory over Kristina Mladenovic in the third round on Friday.

The seven-time champion, 36, who returned in February after giving birth, is second on Centre Court.

Eight-time winner Roger Federer, 36, plays German Jan-Lennard Struff last on Centre in round three.

Five-time winner Venus Williams opens on Court One against Kiki Bertens.

2016 runner-up Milos Raonic, seeded 13, faces 24-year-old Austrian Dennis Novak, who has never progressed past the third round of a Grand Slam.

American 10th seed Madison Keys, the 2017 US Open runner-up who also reached the semi-finals at this year's French Open, will be favourite to overcome world number 120 and qualifier Evgeniya Rodina, who has won five matches en route to this stage.

If Keys wins it could set up an all-American last-16 encounter against Serena Williams.

Sixteen of the 32 men's seeds have been knocked out in the opening two rounds, along with 14 in the women's draw.

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I'm going in the right direction - Williams

Has Williams - the current world number 181- already justified Wimbledon's decision to give her a seeding?

Top-10 seeds Caroline Wozniacki, Sloane Stephens, Elina Svitolina, Caroline Garcia and Petra Kvitova have fallen through the trap door, but veteran Williams reached the last 32 with an impressive 6-1 6-4 victory over qualifier Viktoriya Tomova.

She now faces French world number 62 Mladenovic, whom she defeated in their only meeting at the French Open in 2016.

"It will be good," said 23-time Grand Slam champion Williams.

"I haven't played her in a while. She's had a really good year last year. She's still doing well. I have to come out there and do the best that I can do.

"I feel like I'm going in the right direction. This match was better than my first round. I just hope every match is better."

Federer rematch with Melbourne foe

Defending champion Roger Federer has won 26 consecutive sets at Wimbledon

Swiss Federer looked relaxed and greeted his adoring supporters as he entered the practice courts on Thursday in preparation for Friday's contest against the big-serving Struff.

The 20-time Grand Slam champion, who has not dropped a set since the 2016 semi-finals, will have his returning game tested by a player whom he defeated 6-4 6-4 7-6 at this year's Australian Open.

Struff, quoted in German Bild, said: "I played a good match against Federer in Melbourne. That gives me courage.

"It will be brutally difficult, but I'm looking forward to it."