On July 14, Martina Hingis loses her first singles match of the season to Daniela Hantuchova, her doubles partner on tour last year. (Katherine Frey/The Washington Post)

The problem with Martina Hingis’s story is that it leads to more questions than answers. What if she had never retired in 2003 at 22 or again four years later? Could she still play singles at a competitive level today?

The questions don’t haunt Hingis. She plays World Team Tennis for the Washington Kastles with a smile and an easy-going demeanor. After her second retirement, the 33-year-old got into coaching before returning to the WTA Tour doubles circuit a year ago.

Following a tumultuous and controversial career, tennis is on Hingis’s terms now.

“I would not play if I didn’t feel like I still have it,” Hingis said. “And I proved it.”

Indeed, Hingis won a women’s doubles title at the Sony Open in March with Sabine Lisicki. She said she will pair with Flavia Pennetta for the rest of the year, including the U.S. Open. The goal is to win another Grand Slam.

That used to be expected for Hingis. She won three of her five in singles as a 16-year-old in 1997 — Australian Open, U.S. Open and Wimbledon — and won nine more in doubles. Citing injuries, she retired in 2003 and then returned to the sport three years later. After she drew a two-year suspension for testing positive for cocaine at Wimbledon in 2007, Hingis again retired. She denied taking the drug but did not appeal the ruling.

Named after Martina Navratilova, Hingis couldn’t stay away from tennis for long after her suspension. She did some commentary and then moved into coaching. There was still tennis but without the injuries, the grueling training schedule, the constant travel.

But something was missing: the competition.

While coaching Anastasia Pavlyuchenkova, Hingis paired up with her in a practice set against highly ranked doubles team Ekaterina Makarova and Elena Vesnina . Hingis and Pavlyuchenkova beat them handily, and even though it was just practice, the seeds for Hingis’s return were planted.

“Practice is always different obviously, but it was like, ‘I’m not that bad yet. I could do it,’ ” Hingis said. “That made me come back.”

Daniela Hantuchova , born in the same part of Slovakia as Hingis, urged Hingis to pair up with her for doubles last summer. For Hingis, that was perfect: She would have her competition without the physical commitment required to play singles.

She and Hantuchova lost five of the eight matches they played together before parting ways. They remain good friends, and Hantuchova said she’s glad she played a role in getting Hingis back on the WTA Tour.

“She’s been my idol since I was a little girl,” Hantuchova said. “Playing against her and with her, it’s always so inspirational.”

Hantuchova handed Hingis her first singles loss in World Team Tennis this season when the two played Monday night. Entering the match, Hingis had won 20 of her 22 games in women’s singles, including matches against rising star Taylor Townsend and Vera Zvonareva .

After her second convincing win over Townsend in a week, Hingis talked with her for several minutes, the former coach in her surfacing. Liezel Huber, Townsend’s Philadelphia Freedoms teammate, told Townsend she could learn from Hingis.

“I watch her play every night, and I’m sitting there learning,” said Bobby Reynolds, Hingis’s Kastles teammate. “It’s amazing what she can do with the ball. She has an answer for every single shot. I know she could still play at the top level if she wanted to.”

Hingis has been known to change her mind, but she said a return to singles isn’t in her future. She wouldn’t return if she didn’t think she could win, and in order to win, she would have to “physically suffer” through training and travel for tournaments.

Now Hingis plays what she wants when she wants, only answering to herself.

“Win or lose a point, she just has a smile that gets the crowd into it,” Reynolds said. “You just know that she’s enjoying herself out there.”