It was a day filled with surprises and twists in Cincinnati. These are the Top 5 photos from Thursday's hard-court action.
1. Younger sister Serena was in the crowd cheering Venus Williams to a hard-fought victory. Venus battled from a set down to defeat Donna Vekic, 2-6, 6-3, 6-3, for her fourth quarterfinal appearance of the season. After losing three consecutive openers, the seven-time Grand Slam singles champion seems to be beaming with confidence this week.
2. After defeating his "hero" Kei Nishikori on Wednesday, Japan's Yoshihito Nishioka returned on Thursday with the same intensity to advance past Australia's Alex de Minaur, 7-5, 6-4. Nishioka battled his way through qualifying to reach the final eight at an ATP Masters 1000 event for the first time in his career.
3. "I played 45 matches this year, so I think I should be fine,” said Roger Federer at his post-match press conference. The 20-time Grand Slam champion endured one of the quickest defeats of his career against Russian qualifier Andrey Rublev, who won 6-3, 6-4 after 62 minutes. Federer is still 39-6 this season and will bid for his fourth title of the year at the US Open.
4. Two-time major singles champion Svetlana Kuznetsova was relentless in her Thursday matchup against 10th-ranked Sloane Stephens. Kuznetsova, who has fallen outside of the Top 100 and missed out on defending her Washington DC title due to visa issues, dominated Stephens, 6-1, 6-2, to advance to the quarterfinals. Kuznetsova will have another crack at a Top 10 player on Friday when she takes on world No. 3 Karolina Pliskova.
5. Defending Cincinnati champion Novak Djokovic is one step closer to reclaiming the title after toppling Pablo Carreno Busta 6-3, 6-4. The Serb will look to capture his 35th match victory at the event on Friday against Frenchman Lucas Pouille. In their first meeting earlier this year, Djokovic dismissed Pouille in straight sets in the Australian Open semifinals.