MELBOURNE, Australia -- For six years, as the USTA's czar of player development, Patrick McEnroe developed a clever response to all the moaning and groaning about the sorry state of American men's tennis.

"Yeah," he'd say, smiling, "the 12- and 14-year-olds coming up are very strong."

Invariably, this induced eye-rolling -- and sometimes worse.

Well, wonder of wonders, they're finally here.

Frances Tiafoe, who won his first career Grand Slam match Tuesday, was one of three 20-and-under American men to make the second round in Australia. Robert Prezioso/Getty Images

No fewer than seven U.S. men aged 20 or younger (four of them teenagers) made the main draw of this Australian Open. That's the more than any other country and the most 20-under Americans in a Grand Slam in nearly a decade.

On a sun-splashed day before the tournament began, McEnroe, attired in a snazzy light blue suit, said he was proud of his team and the group of players.

"When I was hired in 2008, I think I said it would be eight to 10 years before we saw the progress at this level," McEnroe said. "Our goal was to produce some good players, top-100 players, players who could get direct entry into the main draws of Slams.

"I think you're seeing those good players coming through now. I think a couple of them might develop into top players."

Tuesday, six of them were in action. Among the highlights:

Frances Tiafoe, an 18-year-old from College Park, Maryland, vaulted into the second round with a four-set win over Mikhail Kukushkin. It was Tiafoe's first Grand Slam victory ever. He joined Noah Rubin, a 20-year-old New Yorker, who beat fellow American Bjorn Fratangelo in five sets Monday and will play Roger Federer on Wednesday.

There were some encouraging signs, but clearly the learning curve remains steep.

"Very disappointing," Donaldson said of the blown two-set lead. "But I can only justify it as a learning experience for so long. It's kind of a cop-out. I had chances to pull that one out.

"Losses like this one really define your character."

Tiafoe, meanwhile, will play ascendant German teenager Alexander Zverev in the second round.

At last year's US Open, Tiafoe squandered a two-set advantage in the first round and lost to fellow American John Isner in a fifth-set tiebreaker.

Isner, the United States' highest-ranked man, at No. 19, said he was impressed with the younger players.

"You're hard-pressed to find another country with guys, 18, 19, 20 who hit the ball as well as our guys," he said.

Back in the late 1980s, there was a competitive group of Americans who grew up in Florida and drove each other to great heights. Pete Sampras, Andre Agassi, Jim Courier and Michael Chang would all go on to win Grand Slams and collect a total of 27 major titles.

Andy Roddick was the last American man to win a major, the 2003 US Open.

While no one is suggesting this group has that kind of potential, there is a certain strength in numbers. Quantity, for the moment, prevails over quality.

"I hope for the best for American tennis," insisted Jack Sock, who is ranked No. 20. "After the success of Pete and Andre and Andy, it was on us.

"The guys around me see those 18-20-year-old guys coming up -- and we want to keep our spots, too."

Michael Mmoh is a melting pot in and of himself, the son of a former Nigerian tennis player and a Irish-Australian nurse. He was born and raised in Saudi Arabia but is a U.S. citizen.

In losing to No. 25 seed Gilles Simon, the 19-year-old said he let a bad warm-up take him out of a proper mindset. He added that the young players welcome the competition -- and the support of their peers.

"It helps a lot," Mmoh said of the competition. "We're all in the same position, especially in tough times. We use each other as a resource. It's a good dynamic."

Mmoh said he was probably headed to the Challenger in Maui, Hawaii, where the purse for the entire field is $50,000 -- or what he made for playing his match in the main draw.

Five years ago, Ryan Harrison was the can't-miss 20-year-old, trying to fill the vacuum in the wake of Roddick.

Harrison was ranked in the 40s and seemed destined for a significant career. Today, his ATP record is 76-107, and he has yet to win a title.

Harrison knows these young fellow Americans well, because he saw a number of them last year in minor league Challengers, when he was trying to raise his ranking that plunged as low as the 190s.

"I've been through the ups, 'You can win Grand Slams,'" Harrison explained. "To the downs, with people writing, 'You're done.'

"You can just get so caught up with results you forget the joy to play at this level. It's been frustrating the last couple of years. Wanting to prove people wrong so bad, I locked myself up with nerves. A lot of guys would have been broken."

Ryan Harrison, once the next big thing in American tennis, remains a cautionary tale for a nation pining to find a star. Jason Heidrich/Icon Sportswire

Instead, Harrison pulled it together late last year, beating Isner in Toronto and Milos Raonic in the US Open.

His advice for the younger players?

"You've got to be your personality," Harrison said. "Commit to who you are. Insecurity led me to the things that happened.

"They're all different. To give them one specific recipe to be good, you can't."

A little over two years ago, at the USTA boys 16 and 18 national championships, there were some familiar faces. Six of the seven American men who made the main draw here reached the quarterfinals in Kalamazoo.

"It's pretty cool to see guys you played with in 10s and 12s come through," Donaldson said. "We're all just trying to get better."

Steve Johnson, who is America's No. 3-ranked man at No. 30, sees good things happening for this group.

"These guys see their peers do it," he said. "And think, why not them?"