Serena Williams herself admitted that she could not even be competitive with the best male tennis players during an appearance on the David Letterman show in 2011 or so.
“Actually it’s funny, because Andy Murray, he’s been joking about myself and him playing a match. I’m like, ‘Andy, seriously, are you kidding me?’ For me, men's tennis and women's tennis are completely, almost, two separate sports. If I were to play Andy Murray, I would lose 6-0, 6-0 in five to six minutes, maybe 10 minutes. No, it’s true. It’s a completely different sport. The men are a lot faster and they serve harder, they hit harder, it’s just a different game. I love to play women’s tennis. I only want to play girls, because i don’t want to be embarrassed. I would not do the tour, I would not do Billie Jean [King] any disservice. So Andy, stop it. I’m not going to let you kill me."
The video of this appearance is still up on YouTube
The fact that it happened concerning tennis is pretty funny. It’s a sport where men and women do compete on the same court. It’s called Mixed Doubles, and it’s very telling. The women struggle to return any serves at all. It’s so silly that our culture is subjected to this stuff, all because of a handful of weirdos.
"It was the 1998 Australian Open and the Williams sisters, Venus and Serena, had seen some of the male players practising. On the basis of what they saw, they were convinced that they could beat a man ranked around 200 in the world and wanted to set up a game. At the time I was ranked 203 so the men's tour manager mentioned the possibility of a challenge to me, thinking that I was the perfect candidate.Preparation is crucial. Remember that a game like this is light-hearted - taking it too seriously would be a mistake. My training regime consisted of a leisurely round of golf in the morning followed by a couple of shandies. I turned up on court feeling suitably laid-back.
My first game of the afternoon, just a one-set match, was against Serena. A hint: try and play your match somewhere quiet, where you're not going to be pestered by big crowds or lots of press - we were out on one of the back courts at Melbourne Park, No 17 I think it was. I felt so relaxed that I didn't even warm up properly. We started playing and I raced into a 5-0 lead.
At this point Venus turned up to watch. She had just finished a press conference after a quarter-final loss against Lindsey Davenport. In the end I won my game against Serena 6-1 but by the time we were at the net shaking hands, Venus was on court, ready to have a go against me as well. The game against Venus was very similar. I ended up winning 6-2." -- Karsten Braasch, German Tennis Professional