Then he watched Roger Federer advance to the finals as well when David Goffin retired in the second set with a shoulder injury. Federer dropped off just once set on his path to the final, against Stan Wawrinka in the quarter-finals, while Djokovic dropped four: against Adrian Mannarino, Grigor Dimitrov, Milos Raonic and Marin Cilic. Djokovic broke Dimitrov to go up 2-1 in the third set, and more rain prompted play to be called off for the night.
Djokovic, a five-time finalist here who has never broken through, is aiming to lift the trophy at the only one of the Masters 1000 series events that he has never won.
"I think also I'm less stressed", she said.
"That's not how I wanted to win, but I'll take it", the Swiss said.
The Swiss, seeking his eighth title in OH, saved all five break points he faced against the German and moves on to a third-round matchup with Argentine Leonardo Mayer.
Several days of rain turned the quarterfinals into an endurance test. We were not the only ones (dealing with interruptions), but it just makes it harder, because you're warming up, you're cooling down. He beat Karen Khachanov in three sets, completing a suspended match, and got a 7-6 (7), 6-4 win over Pablo Carreno Busta, who was playing his only match of the day.
"I feel like I'm trying to defend my title from way back when", he said. I feel and I heard that it's completely different.
David Goffin's semi-final retirement set the pair up for a fourth final match-up in OH, the Belgian forced to withdraw due to arm and shoulder discomfort having trailed by one set. After dropping the first three games of the final set, she took a medical timeout for treatment. Firing 12 aces and having nearly half of his serves unreturned, the Swiss won his 11th consecutive match in Cincinnati.
In the women's bracket, the top-ranked Simona Halep beat Ashleigh Barty 7-5, 6-4 early in the afternoon to reach the quarterfinals, then returned a few hours later and knocked off Lesia Tsurenko 6-4, 6-1, raising both arms in triumph at the end of her long day featuring two full matches. "So before the match, I'm less nervous than I used to be".
Del Potro is facing 11th-seeded Belgian David Goffin, a 6-2, 6-4 victor over sixth-seeded South African Kevin Anderson in another rain-delayed match.
Keys next faces Aryna Sabalenka of Belarus, who upset French sixth seed Caroline Garcia 6-4, 3-6, 7-5. "I just played and waited for the important points to go for the victor". Later Friday, Goffin will play the victor of the match between Juan Martin del Potro and Nick Kyrgios.
The Czech will face Kiki Bertens after the Dutchwoman defeated Ukrainian fifth seed Elina Svitolina 6-4 6-3.