American teenager Madison Keys talks about upsetting Serena Williams when she was just 14 years old in a World Team Tennis encounter.

“I was 14 and we were playing in a World Team Tennis event for Philadelphia Freedoms, the professional players have to come along to promote the event,’’ Keys told The Birmingham Mail. “She obviously wasn’t going full out, it was first to five [games], no advantages, people cheering, your bench is on the side of the court, it was definitely not a competitive match. But I think that was probably one of the best five or six games I have ever put together. I think I hit 10 aces or something, I was serving really well. I think I was just so excited I was not even focusing and I was just going for everything. When it finished I was like ‘Whoa, I just beat Serena Williams.’”

Keys, who reached the Birmingham quarterfinals where she lost to Magdalena Rybarikova today,  will crack the Top 50 for the first time next week. Keys said she thinks that Serena is a big favorite to retain her Wimbledon title.

“She is amazing. We were trying to think of the last time she lost a match and other than when Sloane [Stephens] beat her in Australia," Keys said. "She’s had one loss in months. She plays so well on grass and it suits her game so well, if she is playing well I don’t really know who can beat her.”