It’s a rivalry that goes back many years – back to 2012 and 2013 when Serena Williams defeated Victoria Azarenka in the US Open final.

And it’s about to be renewed tonight in New York when the pair meet for a place in this year’s final.

“I’m so excited about this. It’s an amazing opportunity to play against a champion, somebody who I respect a lot, who is my friend,” Azarenka said of Williams.

Azarenka’s last Slam title was in Australian in 2013 and her last finals appearance was month later when she lost to Serena in three sets.

For Williams, the quarter final win over Tsvetana Pironkova was no walk in the park – a tough three setter that will have taken its toll.

But even at 38 she is as force to be reckoned with – and more so with no Barty or Halep to challenge this year.

“In the beginning, I was a little fatigued, for whatever reason, ” She said.

“I can’t do that if I want to keep winning, so I need to figure that out.”

Williams and Azarenka are the last remaining mothers in the draw after nine started the tournament.

Only three women – Kim Clijsters, Margaret Court and Evonne Goolagong – have won Grand Slam titles in the Open era after having children.