Washington - US top seed John Isner and French second seed Gael Monfils cruised into the third round of the ATP and WTA Washington Open on Wednesday but former world number one Caroline Wozniacki dropped out due to injury while leading.
Isner, coming off heartbreaking Wimbledon and Davis Cup defeats, fired 14 aces and dropped only three points on his first serve in a 6-3, 6-4 romp over Australian qualifier James Duckworth.
"I'm happy I got through my first match. I can get tripped up in those," Isner said. "I'm not looking past anyone."
Flamboyant Monfils, who had lost three matches in a row after suffering a mystery illness, fired 10 aces and lost only two points on his first serves in a 6-3, 6-2 victory over Taiwan's Lu Yen-hsun.
"I played a very solid match," Monfils said. "I was surprised I could play that good so soon and I want to keep it going for the next few matches."
Wozniacki, a two-time US Open runner-up from Denmark, was leading 7-5, 3-4, when a left arm injury forced her to retire from her second-round match against Aussie top seed Samantha Stosur, the 2011 US Open winner.
"It happened at 5-all in the first set," Wozniacki said. "I hit a backhand and I just felt the pain."
Wozniacki, who has battled injuries all year, fought into the second set but could not stand the pain. At 58th, she is out of the world top 50 for the first time since 2008.
"I'll take it and try to run with it as far as I can," said Stosur, who faces US wildcard Jessica Pegula in the quarter-finals.
Next for Monfils is Croatian 16th seed Borna Coric, who downed Japan's Yuichi Sugita 6-4, 6-4. Isner will meet Cypriot 15th seed Marcos Baghdatis, who ousted Australian John Millman 6-2, 6-4, for a quarter-final berth.
Aussie third seed Bernard Tomic fired 12 aces in beating American Donald Young 7-6 (7/4), 6-3 to book a third-round date with Croatian 13th seed Ivo Karlovic, who blasted 19 aces in beating American Brian Baker 6-3, 7-6 (7/4).
Isner and Monfils, who had first-round byes, have split eight career meetings and could play a third time at Washington in Sunday's final. Isner won a 2007 semi-final while Monfils won a 2011 semi-final rematch, both going to a third-set tie-breaker.
"I look forward to playing Johnny," Monfils said. "Every time I come here I play him."
Neither has won the Washington hardcourt crown. Monfils, ranked 17th, lost to Czech Radek Stepanek in the 2011 final. Isner, ranked 16th, lost the 2007, 2013 and 2015 finals.
"To win here would be very special," Isner said. "I've been very close before."
Isner lost a third-round Wimbledon match to France's Jo-Wilfried Tsonga after taking the first two sets, dropping the fifth set 19-17. Tsonga's next foe, compatriot Richard Gasquet, retired after six games, adding to Isner's woes on what might have been.
"It was a very excruciating match for me and even tougher when I landed and found out Gasquet only lasted (six) games," Isner said. "It was a tough pill to swallow."
Adding to his pain was a Davis Cup home loss to Croatia last weekend after the US team took a 2-0 lead.
"You have to try to forget about it," Isner said. "It's tough, though. I haven't forgotten about it. It's hard to forget about it. It's in the back of my mind right now."
Since losing to Rafael Nadal in April's Monte Carlo final, Monfils had withdrawn from Munich with a groin strain, the French Open and Halle with a severe illness, but he blitzed Lu in 62 minutes.
"It has been a tough month for sure," said Monfils. "I didn't do anything but rest. I don't know how I got this thing. They cannot put a name to it. But I feel much better. I feel my ability is back."
German 19-year-old seventh seed Alexander Zverev beat US 18-year-old Taylor Fritz 6-4, 6-2. Zverev, ranked 27th, is the youngest to crack the world top 30 since Nadal in 2005.
"I'm happy with the way I'm playing," Zverev said. "It's a great start to the hardcourts."
Results on Wednesday from the third day of the ATP and WTA Washington Open (x denotes seed):
Steve Johnson (USA x5) bt Adrian Mannarino (FRA) 6-3, 6-4
Gilles Muller (LUX x14) bt Yoshihito Nishioka (JPN) 6-4, 6-1
Alexander Zverev (GER x7) bt Taylor Fritz (USA) 6-4, 6-2
Ryan Harrison (USA) bt Viktor Troicki (SRB x10) 7-6 (7/4), 6-4
Gael Monfils (FRA x2) bt Lu Yen-hsun (TPE) 6-3, 6-2
Ivo Karlovic (CRO x13) bt Brian Baker (USA) 6-3, 7-6 (7/4)
Malek Jaziri (TUN) bt Kevin Anderson (RSA x9) 5-7, 6-4, 7-6 (7/3)
John Isner (USA x1) bt James Duckworth (AUS) 6-3, 6-4
Marcos Baghdatis (CYP x15) bt John Millman (AUS) 6-2, 6-4
Jack Sock (USA x6) bt Lukas Lacko (SVK) 7-6 (7/1), 6-4
Borna Coric (CRO x16) bt Yuichi Sugita (JPN) 6-4, 6-4
Bernard Tomic (AUS x3) bt Donald Young (USA) 7-6 (7/4), 6-3
Yanina Wickmayer (BEL x7) bt Zhang Shuai (CHN) 6-3, 7-5
Jessica Pegula (USA) bt Christina McHale (USA) 7-5, 6-2
Samantha Stosur (AUS x1) bt Caroline Wozniacki (DEN) 5-7, 4-3, retired, left arm
Yulia Putintseva (KAZ x6) bt Usue Arconada (USA) 6-4, 4-6, 6-4
Lauren Davis (USA) bt Shelby Rogers (USA) 5-7, 7-5, 6-3
Kristina Mladenovic (FRA x4) bt Samantha Crawford (USA) 6-2, 2-6, 6-3