Top seeds Rublev and Sabalenka tested in Washington wins
World number eight Rublev fired 15 aces and rallied after a rain delay in dispatching 20-year-old Frenchman Luca Van Assche 4-6, 6-3, 6-4 to reach the last 16 at the hardcourt tuneup for the US Open, which starts on August 26.
"The first set I was playing really bad. I was missing without reason sometimes out of nowhere," Rublev said.
"When you're playing horrible tennis, you feel like today is not your day, somehow you're winning those matches, they are much more special than when you're playing normal and winning much easier."
Two-time reigning Australian Open champion Sabalenka outlasted 78th-ranked Kamilla Rakhimova 7-5, 4-6, 6-4 to reach the quarter-finals.
Third-ranked Sabalenka, who had a first-round bye, is coming off a right shoulder injury that forced her to withdraw from Wimbledon.
She fired 13 aces and 53 winners to win after two hours and 46 minutes.
"Super happy to get this win," Sabalenka said. "It was a really tough match for me, especially as I didn't play for probably a month. That was a tough battle. She played such incredible tennis.
"I had to really fight through it."
Top seed Sabalenka will face either fellow Belarusian double Australian Open winner Victoria Azarenka, seeded sixth, or China's Wang Yafan in Friday's quarter-finals.
Next up for Rublev will be France's 68th-ranked Arthur Rinderknech, the 16th seed who advanced when China's Shang Juncheng retired leading 3-2.
'I was playing horrible'
Rublev is chasing his 17th career ATP Tour title after triumphs this year in Madrid and Hong Kong.
The 26-year-old Russian won his second ATP Masters in May on Madrid clay, the first coming last year at Monte Carlo.
Van Assche, ranked 118th, broke Rublev to seize a 5-4 lead in the opening set and held again on his fifth ace of the match to claim the first set in 42 minutes.
"First set, I was playing horrible," Rublev said. "I missed a lot of easy balls without sense. In the end I start to feel super tight. He start to feel confident."
Rublev led 3-2 in the second set when rain halted the match and hours later when play resumed broke in the eighth game and took the set on his 11th ace.
"The rain delay, I was able to calm myself down, think about the match, understand what I was doing wrong," Rublev said.
Rublev broke for a 3-2 edge in the third set and served out to win.
Sabalenka broke in the 11th game and held to capture the first set in 67 minutes.
The 22-year-old Russian Rakhimova broke in the final game of the second set on Sabalenka's 41st unforced error to force a decider.
Rakhimova sent a forehand wide to surrender a break in the seventh game of the last set and Sabalenka held twice to win.
"I was trying to keep focusing on myself in those key moments, trying to stay focused and aggressive and put as much pressure as I can on her," Sabalenka said.
Britain's 21-year-old Emma Raducanu, the 2021 US Open champion, beat American Peyton Stearns 7-6 (8/6), 6-2 to reach the quarter-finals.
"I'm very pleased with how I managed to come through that," Raducanu said.
