Andrea Petkovic looked across the tennis court Monday night and loved what she saw: a 16-year-old girl, her ear buds in, bouncing around to music.

Never mind that Petkovic, an eighth-year professional from Germany, was getting ready to give that girl, Taylor Townsend, another unforgiving lesson about the grinding life of making a living in this sport. Petkovic, 25, just found Townsend’s energy so endearing.

Monday’s Family Circle Cup first round was Townsend’s sixth professional match, in her fourth event. Last year, she became the first American to finish No. 1 in the world junior girls rankings since 1982. She turned pro this year surrounded by anticipation that players like her and Sloane Stephens, a more advanced 20-year-old, could be the future of United States women’s tennis, as Venus and Serena Williams enter the latter stages of their careers.

But on Monday, Townsend never came close to her third victory, falling 6-3, 6-0 in a 1-hour, 16-minute match. Her 105-mph left-handed serve looked overpowering in some moments, but she showed the emotional inconsistencies of a teenage player in others, as she hit return shots well long and, after one error, swatted a ball into the green clay out of frustration.

Petkovic, who two years ago was ranked 10th in the world, fell behind 2-0 in the first set, knotted the set at three games apiece, and then won nine straight games to close. After falling behind 2-0 in the first set, Petkovic thought, “OK, that was a little bit more than I expected. I figure with (Townsend being) 16, you’re not going to hold this level.”

Townsend couldn’t. But this is where all tennis prodigies begin as pros, with glimpses of greatness, but inevitably, many humbling early-round exits in front of few fans. Serena Williams remembers her first match, in 1995, lasting less than an hour. She earned $240 for it. Samantha Stosur recalls “a very daunting process, but obviously one that you’ve got to go through.”

Townsend already endured an ordeal last year, when the United States Tennis Association refused to pay her travel expenses to tournaments, including the U.S. Open, until she got in better physical condition. Townsend’s mother paid her way to the Open, and she made the junior quarterfinals. The USTA later apologized and reimbursed Townsend’s Open expenses.

The association’s decision angered full-figured players like Lindsay Davenport and Serena Williams, who excelled while bucking the notion that only svelte women can win. Like Townsend and Stephens, Williams is black. She and Venus helped open the sporting world’s eyes to diverse-looking tennis players. Davenport wrote on Twitter that USTA’s ultimatum “disheartened” her. Williams on Monday said it “was just shocking and unnecessary.”

Though the decision stung Townsend, she said it also “really showed me, yeah, you weren’t in the best shape.” She prepared for this season by working out with a trainer, Danny McNair, whose methods baffled her at first. For one exercise, he had her backpedal on an inclined treadmill while jumping and hitting serves.

“I was scared for my life,” Townsend said, laughing about it now.

Townsend also improved her diet. She avoided chocolate and no longer put cookie dough on frozen yogurt — a tough change because she loves sweets. Now, she consults a nutritionist.

“When I feel like, ‘Oh my God, I want something sweet, I call her and she talks me out of it,” Townsend said.

At the Family Circle Cup players’ party Sunday, Townsend’s newfound professional discipline intersected with her natural teenage exuberance. She arrived at the event wearing a fancy green dress — and pink rabbit ears on her head. The party included a table of candy, but Townsend didn’t partake because of her diet, and also because she didn’t want anything to get stuck in her braces.

The hard choices are paying off. She feels like she is moving better on the court. She wants to be a role model for teenagers who struggle to get fit. But her coach, Juan Todero, said he wants to see a more mature playing style, too, because “she has to control the moments of the match much better.”

Monday was another difficult step from potential to results, the same one all the greats had to make. But Petkovic felt enough power in Townsend’s shots that when she met Townsend at the net after the match, she told her, “Girl, you’re going to be big later on. But please wait until I’m done.”