Serena defeats Venus to sustain Slam bid at US Open

Serena Williams, pictured, goes into a semi-final against Italy's 43rd-ranked Roberta Vinci after beating sister Venus during their 2015...

Serena Williams, pictured, goes into a semi-final against Italy's 43rd-ranked Roberta Vinci after beating sister Venus during their 2015 US Open Women's quarterfinals match in New York on September 8, 2015

NEW YORK - World number one Serena Williams, chasing the first calendar Grand Slam since 1988, advanced to the US Open semi-finals by defeating 23rd-seeded sister Venus 6-2, 1-6, 6-3.

Three-time defending champion Serena reached a Thursday semi-final against Italy's 43rd-ranked Roberta Vinci, who eliminated France's 40th-ranked Kristina Mladenovic 6-3, 5-7, 6-4.

The two met as recently as July at Wimbledon, where Serena claimed one of many routine wins in the rivalry, which often fails to live up to the hype.

"The only player in the draw I don't want to play, not only because she's my sister, but for me she's the best player," Serena said of Venus before their clash.

"She has beaten me so many times. She's a player that knows how to win, knows how to beat me and knows my weaknesses better than anyone."