NEW YORK -- Juan Martin del Potro's victory at the U.S. Open last year signaled that a new generation night be ready to make its mark in the men's game, a feeling that only intensified when fellow 21-year-old Marin Cilic reached the semifinals of the Australian Open in January.
But 12 months after his big win, del Potro finds himself unable to defend his title after having wrist surgery in May. His contemporaries have also failed to have much of an impact. Are any of them ready to step up over the next two weeks?
Two of the leading hopes will face off in the second round of the U.S. Open on Wednesday when Cilic meets 20-year-old Kei Nishikori. Both have displayed their potential here in the past. Nishikori reached the fourth round in 2008 at 18, losing to del Potro in an entertaining contest. Cilic gave Novak Djokovic a scare in 2008 and made the quarterfinals last year, losing to del Potro after defeating Andy Murray. But these early indications of promise have yet to fully materialize.
Instead of building on his stellar start to the season, Cilic has been up and down -- with the odd highlight, but also with several first-round losses, including at Wimbledon as well as the Toronto and Cincinnati Masters leading up to the U.S. Open.
Tall, serious and hard-working, Cilic idolized Wimbledon champion Goran Ivanisevic growing up but has said his personality is the "opposite" of the mercurial Croatian hero.
Instead of smashing rackets like Ivanisevic, the 6-foot-6 big-serving Cilic is philosophical about his season so far. "I was trying to do everything I could to become better and do better, but unfortunately things were not going as great as in the beginning of the year," he told ESPN.com. "But I take that as a good experience.
"It takes also a lot of courage to come through that, and when everything is going well it's always easy to play, but when things are not as good, it's important to stay in it and to fight there."
He will not elaborate upon what has plagued him, only saying: "It was mentally some things [that] didn't click the way they should, and it's tougher to get the right result.
"I hope that this period, after that, is going to make me stronger and better and I'm going to bounce back up."
Nishikori's troubles have been physical. He missed almost a year with problems in his right elbow, eventually undergoing surgery last August and returning this February. "I couldn't move my right elbow for two, three weeks," he said of undergoing surgery. "It was really tough moment. I started hitting with [my left hand], doing rehab."
The only positive was that it allowed the oft-homesick prodigy to return home to Japan for his first extended stay since moving to Florida to train at 14.
He has won three challengers since, including Binghamton three weeks ago, but his first-round win at the U.S. Open was only his second ATP-level win of the year. But he says he's now feeling "100 percent" and is ready for more, having come through qualifying and earned a quick first-round win when his opponent retired.
"I started winning challengers and get some confidence tennis-wise and body-wise, too," said the speedy 5-10 Nishikori, adding that the injury has made him take greater pains to try to stay healthy from now on. "I start thinking more of my body. All the little things, I start doing it -- all the stretch[es], taking care of my body."
Cilic and Nishikori are anticipating a tough faceoff when they meet Wednesday, and both enjoy competing at Flushing Meadows. "This [Grand Slam] is the toughest one because conditions are varying from day to day and it's really windy, gets as hot as today, you can play during the night," Cilic said. "It's not easy to adjust, but I like it."
Nishikori, who has admitted being "scared" of locals when he first moved to the United States, has come to enjoy the atmosphere. "I like this court and the balls," he said, adding, "I like the situation here. People are nice here. Loud crowd, it's fun."
Nearby in the draw is another 21-year-old trying to put growing pains behind him. Thiemo de Bakker is a 6-5 Dutchman that Cilic is familiar with from his junior days. De Bakker was the No. 1 junior in 2006 and collected a slew of minor league titles at this time last year. This season, he has begun to make an impact at the ATP level, collecting his first top-10 win over Jo-Wilfried Tsonga on his way to reaching the semifinals in Barcelona and making the semifinals at New Haven last week.
Tight-lipped and sometimes moody, de Bakker only began to pursue tennis seriously at 17 or 18, having coasted through the juniors. "I didn't really work for it," he told ESPN.com earlier this year. "Everything went too easy so I didn't want to practice hard. And from that moment I really started to practice."
He has not taken on a full-time coach, working with Rohan Goetzke of the Dutch tennis federation and Mats Merkel from the adidas player-development program.
The older and mid-20-somethings -- led by Roger Federer, Rafael Nadal and Andy Murray -- are setting the pace for the competition at this year's U.S. Open. But a year after del Potro struck the first blow for the young guard, a group of slightly older, slightly wiser up-and-comers are hoping to follow in his footsteps.
Kamakshi Tandon is a freelance tennis writer for ESPN.com.