Defending champion Sloane Stephens crashed out of the US Open in the quarter-finals, but Serena Williams made it through to the semis as she continues to chase tennis history.
In stiflingly hot conditions, American Stephens went down 6-2 6-3 to Latvian Anastasija Sevastova, who is through to her first grand slam semi-final.
Williams, though took revenge against Karolina Pliskova to set up a US Open semi-final against Sevastova.
Pliskova was the last player to beat Williams in the tournament, in the last four two years ago, and the American made it clear ahead of the match that that contest had played on her mind.
Williams made a nervous start and Pliskova had chances to lead 4-1, but could not take them and paid a heavy price. Williams wobbled again in the second set but served her way out of trouble before clinching a 6-4 6-3 victory.
She said: "I really feel like right now I'm playing free because I was having a baby this time last year. I'm going to enjoy it the best I can."
Following Sloane Stephens' exit, Williams is the only former grand slam champion left in the draw and her status as the favourite to win a record-equalling 24th singles title increases with every passing match.
Pliskova's demise, meanwhile, means none of the top 10 seeds will be present in the final rounds of the tournament for a second consecutive slam.
Sevastova downs Stephens
28-year-old Sevastova retired in 2013 after a succession of injuries drained her motivation. She spent two years studying leisure management but returned to tennis once she felt fully healthy.
She has had her best results in her second career, particularly in New York, where she has now reached the quarter-finals twice and the semi-finals once in the last three years.
Sevastova said: "It was an amazing journey, this three, four years. Right now you're in the tournament, you're playing next tournament next week, and you don't feel it.
"But in the end it's amazing, yes? You can't believe. So, after I stop, at some point I will look at it and I will be proud of myself, for sure.
"I hope I will enjoy it, playing semi-finals. It's not every day you play semi-finals of a grand slam."
Stephens and Sevastova met at the same stage last year, with the American coming from a break down in the final set before winning on a deciding tie-break. It was arguably the closest she came to defeat in her remarkable run, but this time she could not extricate herself from her predicament.
Stephens proud of title defence
Sevastova is one of the wiliest players on tour, mixing up slices, spins and angles and generally making life very uncomfortable for a player like Stephens who feeds off consistency of pace.
Stephens saved two match points but not a third and later revealed she has been suffering from a sinus infection for two days.
She said: "I think today I just really couldn't get anything to connect. Even when I did have my break opportunities, I just wasn't playing the points well at all. It just was a really tough day. The heat doesn't make it any more fun. The better player won."
Stephens was proud of the way she defended her title and will now hope to fare better during the Asian swing than she did last year, when she failed to win a match for the rest of the season.
The 25-year-old said: "The fact that I made it to the quarter-finals and played some really good matches and I just competed as hard as I could, there's a lot to be proud of.
"Obviously defending a title is very hard. I'm not going to dwell on it. Just keep building. There's four more tournaments left. I'm just going to try to play the rest of the season as hard as I can and hopefully have some more good results."
