Fresh from an agonizing defeat at the hands of former junior No. 1 Anastasia Potapova at the Prague Open last week, Zhu Lin showed no signs of a hangover at the Citi Open on Monday night. 

The 28-year-old Chinese sailed through the first round with relative ease after swatting aside Britain's Harriet Dart 6-4, 6-3. The pair split their previous two encounters, and it was Dart who conquered Zhu when they last met at Miami Open last year. 

But Zhu calmly exhibited her dynamic returning and smooth serve this time around, tearing apart Dart, who had failed to show the high-flying form that saw her power into the fourth round of Indian Wells earlier this year.

Next up for Zhu is the winner of the tie between Estonian Kaia Kanepi and Belgian Greet Minnen. Sixth seed Kanepi, who has won four singles titles on the WTA Tour, is the odds-on favorite to come out on top and could provide a much sterner test of Zhu's credentials.

Meanwhile, the reigning U.S. Open singles champion Emma Raducanu was thrashed in her first ever professional doubles match.  

The British No. 1 and fellow Danish teenager Clara Tauson were eliminated in the opening round of the Citi Open by Romanian veteran Monica Niculescu and her Czech partner Lucie Hradecka 6-4, 6-1 in a one-sided affair.  

It was Raducanu's first outing since her disappointing defeat to Caroline Garcia in the second round of Wimbledon.  

The latest setback means Raducanu will shift her attention to the women's singles event. She will face American qualifier Louisa Chirico on Tuesday. 

On the men's side, two-time Wimbledon champion Andy Murray was stunned by world No. 115 Mikael Ymer 6-7(8) 6-4 1-6 in a marathon match that lasted two hours and 50 minutes.  

It was Murray's first Citi Open tie in four years, and the 35-year-old struggled against his Swedish opponent. But Murray insisted he still sets sights on the U.S. Open, this year's fourth and final Grand Slam. 

"There's a lot of people that feel like maybe I shouldn't be playing," said the former world No. 1, who has been plagued by injuries in recent years. 

"But I love tennis, and I love competing. And I feel like I can get better than where I am today. If I reach that point where I don't feel like I can improve or that things are maybe going backward, then that would maybe change where I'm at. 

"I love this sport. That's essentially why I am back and why I wanted to keep going: because I love the sport. There's a lot of people that feel like maybe I shouldn't be playing."