In the 18-minute shutout of the first set, Kanepi's strokes were off and Williams' were pretty much flawless as she grabbed 24 of 30 points.
"Winning a big game and a very important game and a really tight game, I think it was just a relief", said Williams, who took control with a break in the next game and maintained that advantage until she fired a forehand victor on her first match point. "I'm going to do it the best I can", she added. "He hits the ball strong and has a big serve", said the world No.1.
After dismissing her sister in the previous rounds for the loss of just three games, Venus described it as the best her sibling had played against her in thirty matches.
"And I don't think it was capable of going up, because if it was at a 10, I was at a 15 or a 20 - and I'm still there".
When he came back, obviously we had to analyze what has happened in the last 12 months that we were not together and try to understand the situation with my body, with my game, where we are at so that we can, you know, get it to the most satisfying levels that we are looking for.
Along with Kaepernick, she also praised another former San Francisco 49ers player, Eric Reid, after the pair showed up at the U.S. Open on Friday. She returned to Grand Slam tennis at the French Open in May, withdrawing before a fourth-round match with Maria Sharapova due to a pectoral muscle injury.
Williams, the 23-time Grand Slam champion seeking a first major since a 2017 Australian Open title won when she was pregnant with her daughter Olympia, will take on Karolina Pliskova for a semi-final spot after the eighth-seeded Czech beat Australian Ashleigh Barty 6-4, 6-4.
Williams is not longer just a tennis player, but a tennis playing mother.
But after compiling 14 winners and only two unforced errors in that set, Williams began making mistakes, becoming less and less comfortable as Kanepi grew increasingly so.
"We've been waiting to see Serena at the level she was at before her pregnancy".
It certainly was. And that chase-down, turn-around, hook-shot of a passing victor showed a glimpse of how the No. 3 Stephens can go from defense to offense with flair, as she did repeatedly during her 6-3, 6-3 victory over No. 15 Elise Mertens of Belgium in the fourth round. So I have some weapons, too. Nadal leads the series 7-3.
"She got there for a reason, she has a lot of strong parts to her game", Williams said.