Taylor Townsend returns a shot Sunday in qualifying for the Citi Open, which begins Monday at the William H.G. FitzGerald Tennis Center. Townsend advanced to the main draw. (Kelyn Soong/The Washington Post)

Taylor Townsend has noticed improvements in her game ever since she began working with her new coaches last September — not in her technique or shot selection but in her mental game, an area the 18-year-old admits is her weakness.

Townsend kept her negative thoughts to a minimum Sunday and overpowered Czech Tereza Smitkova, 6-3, 6-4, in the second round of the Citi Open qualifying tournament at William H.G. FitzGerald Tennis Center, giving her a spot in the main draw.

Townsend, ranked 145th, will play Germany’s Julia Goerges in the first round Monday night.

“I haven’t really touched anything in my physical game,” said Townsend, who started working with former world No. 4 Zina Garrison and Chicago-based Kamau Murray after the U.S. Open last year. “We just focus a lot on the mental side of things. And that’s basically where all my success has come from.”

Townsend, a heavy-hitting left-hander, employed her full arsenal against the 98th-ranked Smitkova during their 1-hour 28-minute match, whipping forehands past the Czech and hitting drop shots that left her opponent stranded at the baseline.

“It would’ve been really easy to get frustrated because she’s a great ball striker and great server,” said Townsend, who reached the third round of the French Open this year. “I was trying to dictate as much as I could from the ground and trying to move forward.”

Townsend could have unraveled in the second set, where she was broken early to fall behind 2-1. With the majority of the crowd behind her, Townsend stayed positive and referred to the notebook she keeps in her tennis bag for “pointers and tips” during the changeover and regrouped. In the ensuing games, she ran down shots and painted the line with her booming forehand to take a 4-2 lead. Townsend closed the second set and match with an unreturnable second serve.

“It’s a routine,” Townsend said about reading her notebook. “Everybody has a routine, and that’s my routine. I do it not only because it’s my routine but because sometimes you need reminders.”

A year ago, Townsend — who splits her time between the District and her home town of Chicago — was posing with the Citi Open women’s doubles finalist trophy with partner Eugenie Bouchard of Canada.

Bouchard, who withdrew from the tournament with a right knee injury, has become a marquee player and fast-rising star on the WTA, having reached at least the semifinals in the past three Grand Slams, including a runner-up finish at Wimbledon.

“I’m really proud of her,” Townsend said of the 20-year-old she considers a good friend. “With her doing it, it just shows that anyone can do it. If you really put in the hard work and dedication and you believe in yourself like she does and that you know that you belong out there, it can happen.”

Dimitrov withdraws

No. 3 seed Grigor Dimitrov of Bulgaria withdrew from the tournament Sunday because of sickness. A doctor diagnosed the flu and a sinus infection, according to the tournament’s news release.

The Wimbledon doubles champions, American Jack Sock and Canadian Vasek Pospisil, withdrew from doubles tournament to focus on their singles matches. Sock, ranked 72nd in the world, plays Germany’s Michael Berrer in the first round; Pospisil, the No. 13 seed, has a first-round bye. . . .

American Tornado Alicia Black, 16, beat Britain’s Emily Webley-Smith, 6-3, 6-0, in under an hour to reach the main draw of a WTA tournament for the first time in her career. . . .

Seventeen-year-old Jared Donaldson of Rhode Island will play in his first ATP main draw match after beating former college doubles all-American Sekou Bangoura, 6-3, 6-1.

The other Americans advancing to the main draw are Alex Kuznetsov, who defeated wild-card Jordi Arconada of Argentina, 3-6, 6-0, 6-1; former top 100 player Rajeev Ram; and 2005 U.S. Open semifinalist Robby Ginepri.