Though reluctant at first, CoCo Vandeweghe is becoming a formidable doubles player

NEW YORK – At the beginning of the year, CoCo Vandeweghe struck a deal with her coach, Craig Kardon: If she wins a Grand Slam doubles title or reaches the quarterfinals in partner-play at all four Slams, she can retire from doubles. At the U.S. Open this weekend, Vandeweghe has a chance to carry out her end of the deal.

“I take singles very seriously, and that’s what I want to be doing,” Vandeweghe says. “It’s quite funny—I don’t really even want to play doubles.”

Her aversion to the discipline hasn’t stopped her from winning at this year’s U.S. Open. Vandeweghe and Rajeev Ram are in Friday’s mixed doubles final, and the 24-year-old American and Martina Hingis will play in a women’s doubles…