Spain’s Rafael Nadal bites the trophy after winning the final of the French Open tennis tournament against Serbia’s Novak Djokovic at the Roland Garros stadium in Paris.

June 8, 2014 Spain’s Rafael Nadal bites the trophy after winning the final of the French Open tennis tournament against Serbia’s Novak Djokovic at the Roland Garros stadium in Paris. Darko Vojinovic/AP

Rafael Nadal blasted his serve toward Francis Tiafoe’s forehand with so much spin that the ball actually arrived, a split-second later, on the teenager’s backhand side, leaving him so jammed up that he couldn’t put it in play.

That was how the point started Tuesday on a leafy side court at Roland Garros, where the eight-time French Open champion had invited the tournament’s top-seeded junior to serve as his hitting partner.

It was the lone competitive point of a 90-minute workout that had been all business, with the Spaniard going through four shirts and three rackets as he drilled every shot in his arsenal — forehands, backhands, volleys, lobs, service returns and serves. And it was Nadal’s way of thanking Tiafoe for playing the role of human backboard during his pursuit of a 14th Grand Slam title.

“Just to be across the net from him, just handling the ball is an exciting day for me,” said Tiafoe, of Riverdale Park, whose quest for a first junior grand slam championship died with a second-round loss Monday.

As the victors moved on, the 16-year-old Tiafoe wasted no time sulking.

Francis Tiafoe literally grew up around tennis, often spending nights at a Maryland tennis center where his father worked. At only 16, he is ranked number two in the world. Could a future U.S. champion be in the making? (Lee Powell/The Washington Post)

“I’m obviously not happy about it,” Tiafoe said the morning after his defeat to unseeded German Jan Choinski. “It didn’t go how I wanted it to go. But there are bumps in the road. You have to get over them and start working hard.”

Tiafoe punched in at Roland Garros at 8:30 a.m. Tuesday for an hour-long lesson with Patrick McEnroe, the U.S. Tennis Association’s general manager of player development, which proved more of a schooling than he anticipated. A 1989 French Open doubles champion, McEnroe worked Tiafoe side to side, feeling out the power and consistency of his strokes before suggesting he use his left wrist to get more torque on his two-handed backhand and urging more punch in his groundstrokes.

“Ah ha! See that ball?” McEnroe barked as Tiafoe fired a backhand with genuine zip. “It was hard and spinning! Much better!

“Feet! Use your legs!

“More action! Hit it!”

After a 90-minute break, Tiafoe headed to Court 4 for his session with Nadal, which proved both an honor and a preview of how far he has to go before he’s ready to compete with the game’s elite.

Nadal arrived with the fingers on his left hand heavily taped, as if ready for a match, accompanied by his uncle Toni, his longtime coach, as well as his physical trainer, agent and business manager. He started by tugging on resistance bands to warm up his forearms, upper arms and shoulders.

After a few minutes, he signaled he was ready to hit, and the exchange of groundstrokes that followed quickly escalated in tempo, power and velocity.

Soon Tiafoe was standing four or five feet behind the baseline, and it was all he could do to run down the balls that danced mid-flight, landed like an anvil and bounced shoulder-height. Nadal crushed any shallow ball and sent others careening well beyond Tiafoe’s long reach.

There is nothing extraneous in a Nadal practice. There is no wasted motion, no small talk, no joking around and no half-hearted effort. Even water-breaks are efficient.

He asked Tiafoe for shots to his backhand, which he drilled over and over as his uncle critiqued form and follow-through. He asked for shots to his forehand, and fired blast after blast, pausing only for a broken string and a clarification.

“Was out?” Nadal asked after hitting a rare, imperfect forehand.

Tiafoe nodded.

“A lot? Or how much?”

By 1 p.m. Nadal was on his fourth shirt and jogging around the court picking up any stray balls his uncle had missed. He asked Tiafoe for volleys, then overheads. Then he went to the baseline to work on his serve.

“I thought I was hitting pretty well,” Tiafoe said later. “Unless he went for a winner.”

But the biggest revelation about the world’s best clay-court player, in Tiafoe’s eyes, was how hard he worked at improving in the middle of a tournament he has won eight times in nine years.

“He steps into every forehand in practice!” Tiafoe said. “I think him working on his game during the tournament is a big deal. Even at his level, he’s still trying to get better.”

That’s the message McEnroe sought to deliver earlier in the day: to practice with purpose, pay attention to detail and make a habit of all-out effort.

Tiafoe arrived at the Junior French Open as a highly touted phenom, a No. 1 seed in his tournament debut. But the youngster heralded as the future of American tennis ran headlong into a bigger, harder-hitting German who no doubt aspires to being the future of German tennis — just as the other 62 juniors in the field aspire to being the future of Brazilian tennis, Korean tennis, Russian tennis and so on.

“There’s no rush,” McEnroe said of Tiafoe. “He just turned 16. I take it as a very positive experience for him to come over here. He’ll learn from it; he’ll get better. Forget the hype. It’s all about getting better.”