Harmony Tan admitted she feared the prospect of facing a 23-time grand slam winner after defeating Serena Williams at Wimbledon on Tuesday.

It took Tan three hours and 11 minutes to claim the scalp of the seven-time Wimbledon winner, eventually winning the match 7-5 1-6 7-6 (10-7).

The SW19 debutant twice broke back in the third set, even setting up a match point which Williams saved before the eventual tie-break, and rallied from a 4-0 deficit in the tie-break to emerge victorious.

Despite the resolve shown and delight with the win on Centre Court at the All England Club, the 24-year-old revealed she nervously came into the contest.

"[Serena] is a superstar and when I was young I was watching her so many times on the TV," Tan said post-match. "For my first Wimbledon, it's wow. Just wow.

"When I saw the draw, I was really scared. Because, yeah, it's Serena Williams. She's a legend and I was like, 'Oh my God, how can I play?' If I could win one game or two games, it was really good for me.

"I would like to thank everybody today and my team and my coach Nathalie Tauziat, who also played Serena. Thank you so much for being with me."

Tan will now face 32nd seed Sara Sorribes Tormo, who defeated American qualifier Christina McHale 6-2 6-1.