Venus Williams beat her younger sister Serena 5-7, 6-1, 6-0 on Thursday to reach the Sony Ericsson semifinals.

“I just couldn’t keep a ball in play,” Serena said after the match. “Everything was off.”

Even though Serena is nationally recognized as the better tennis player between the two, they are now tied 9-9 in career matchups.

Serena got the best of her older sister in the U.S. Open quarterfinals earlier this year but Venus won their title match at Wimbledon.

Despite Serena’s latest lost she will still have a chance to advance to the semifinals if she can beat Elena Dementieva on Friday.