"Andy, your legs are jelly."
The frustration in Andy Murray's voice was apparent as he berated himself yet again beneath the hot August sun at Louis Armstrong Stadium in the USTA Billie Jean King National Tennis Center.
After a vigorous and lengthy exchange of power ground strokes with Stan Wawrinka, Murray had been caught flat-footed on Wawrinka's next serve, dumping it into the net.
Murray was unhappy with his footwork, but he was not particularly concerned about the score. After all, this was merely a Tuesday afternoon practice session, nearly a full week before Murray will play for keeps at the 2014 U.S. Open.
The Open lets fans in free the week before the tournament to watch qualifying matches for those on the professional fringes. But one of New York's best-kept secrets is that many of the top players are also in attendance, hitting with their coaches, practice partners and other top players, often in front of a tiny but enthusiastic crowd.
The schedule on Armstrong for Wednesday, always subject to change, includes Maria Sharapova and Murray again. (On Arthur Ashe Stadium, which is closed to the public, Novak Djokovic will trade shots with Marin Cilic, and Roger Federer will practice, too.) "I like it and the public seems to like it as well," Murray said Tuesday.
There is no dramatic tension, but there is a certain purity in the tennis with the players free of nerves and letting it rip on almost every shot. The fans appreciate the tennis and put aside their rooting habits, so only the most electrifying points generate more than a smattering of applause.
"I learn from watching them," said Vince Sellers, 16, a junior player who comes each year from the Philippines. "You see how you play in practice, too, giving it your best every shot."
His father, Vernon, said there were other appealing factors. "You get to sit very close to the court and you don't have to pay anything," he said.
Many of the practice matchups feature countrymen - Frenchmen Gael Monfils and Richard Gasquet, Russians Mikhail Youzhny and Evgeny Donskoy - but Murray said players also hit with any peers with whom they are friendly.
"We tend to hit with players that we get on with," said Murray, who is also scheduled to hit with Djokovic on Thursday at Arthur Ashe. "I just talked to Stan, whose practice session was after mine, and asked if he wanted to hit."
After the draw is announced, Murray said, players will seek out partners whose style resembles scheduled opponents. But he said players do not worry about revealing any secrets like new shots or potential weaknesses to their friendly foes.
"You are practicing for yourself - it's about what you need to work on, so I can't worry about Stan," Murray said before gently advising a fan getting ready to snap his picture that "you might want to take the lens cap off."
Although Murray and Wawrinka are friendly, they did not exchange a glance during their crossovers. Murray did sneak in one between-the-legs shot, and the players made all their own calls fairly casually (entourage members retrieved the balls), but they pounded their baseline shots and attacked with their serves "as if it was a semifinals match," said Ben Schragger of Hopewell, New Jersey.
Schragger has been attending the Open with his grandmother Cheryl Vecchiolla for 12 years; a friend told her about these practice sessions five years ago. "I'm a big autograph guy, and you have more access to the players," Schragger said.
Children line up near the court near the end of the sessions thrilled not to be shooed away by ushers.
"Fifteen years ago nobody knew about this," said Yelitza Graterol of Howard Beach, who did know because her husband is a tennis coach. "It was just people in the tennis world. Now, forget about it. There are much bigger crowds."
Bigger is relative, of course. Murray and Wawrinka drew in the low three figures, though that was more than those watching the 24th-ranked Youzhny hit with the 119th-ranked Donskoy at the Grandstand or Michael Llodra hitting with a practice partner.
Not everyone plays in front of even this small a crowd: The USTA works to accommodate players who prefer practicing privately on Ashe, like Sharapova on Tuesday. The schedule also fluctuates. The dynamic Monfils and Gasquet were scheduled for Armstrong but left a disappointed crowd that belatedly discovered they had switched to the privacy of Ashe.
"I don't know why we moved," Monfils said. "Richard invited me to play, and he made the choice."
Monfils was as colorful as ever even without an audience, teasing his friend, pumping himself up loudly after Gasquet misses as if they were in the fifth set of the finals, flinging his racket 50 feet after Gasquet made a great volley and he failed to finish the point, and at one point leaping into the empty stands and running through the seats giving high-fives to imaginary fans.
Although they sat together during breaks, with Monfils throwing his arm around Gasquet or tousling his hair, the two got into a heated argument near the end, though Monfils would not reveal the topic. "We are like children, it was stupid," he said.
Monfils said that while he would have loved performing for the crowd, he was happy to have a chance to practice on Ashe. "It's good to get a feel for the different courts," he said. "I played on Armstrong yesterday. It helps when the tournament starts."
Llodra, who has won three Grand Slam doubles titles and is now a wild card in the singles, agreed. He played on Armstrong on Tuesday but scheduled practices for the Grandstand and the outer courts as well. On Armstrong, after a full practice, he put in an extra half-hour of playing some gentle points with his 6-year-old son, Teo, whose impressive skills and all-out hustle earned him some of the day's biggest cheers from the few fans remaining.
"It's fun getting to hit with him, too," Llodra said.
© 2014 New York Times News Service