JUDY WOODRUFF: Plenty of new thrills at this year's U.S. Open.

On the men's side, Rafael Nadal is still in. Roger Federer is out.

But the big news this year is the success of American women. With the legendary Serena Williams absent — she delivered her first child last week — four others stormed into the semifinals.

The other great Williams sister, Venus, joined by three new to this grand stage, Sloane Stephens, Madison Keys, and CoCo Vandeweghe.

It's the first all-American semifinals since 1981. And it's quickly rewriting the story of American tennis.

Jeffrey Brown reports from Flushing Meadows, New York.

JEFFREY BROWN: Not even U.S. tennis officials dared predict this. Last week, outside the Arthur Ashe Stadium, where the biggest matches are played, I talked to USTA player development director Martin Blackman.

So, how soon before we see another U.S. Open American champion?

MARTIN BLACKMAN, Player Development General Manager, USTA: I'm not going to put myself on the spot for that one.

JEFFREY BROWN: You're not going there for me?

MARTIN BLACKMAN: But I would say between three and five years, we're going to see American women on this court on the final Saturday.

JEFFREY BROWN: Who are not named Williams.

MARTIN BLACKMAN: Who are not named Williams.

JEFFREY BROWN: Yes.

MARTIN BLACKMAN: And we're going to see American men on that court.

JEFFREY BROWN: Blackman was way off with the women, with Venus Williams, joined by three other Americans making their first ever appearance on the semis here.

As for American men, that will have to wait. Just one, Sam Querrey, made it as far as the Round of 16.

In fact, no American man has won here since Andy Roddick in 2003, the last Grand Slam title won by an American man. It's a long drought that American tennis officials are determined to end.

MARTIN BLACKMAN: It's so important.

JEFFREY BROWN: You need that.

MARTIN BLACKMAN: Oh, it's so important. We need American players in here rocking the house, you know, the way Jimmy Connors did, John McEnroe, Agassi, Sampras, the demonstration effect for young people.

Those were household names, American sports heroes, honored on the wall of champions here at the Flushing Meadows, Queens, home of the U.S. Open.

More recently on the men's side, almost all European winners, especially the four greats who have dominated the sport for more than a decade, Roger Federer, Rafael Nadal, Novak Djokovic, and Andy Murray.

JAMES BLAKE, Former Tennis Professional: It has really been difficult for anyone to rack up more titles or Grand Slams outside of them. So, it was just a little bit of a tough situation to be in.

JEFFREY BROWN: James Blake knows first hand just how tough. Retired since 2012, he reached a top ranking of number four in the world in 2006. But he beat Federer just once in 11 tries.

Do you think tennis lost its power in the culture of not getting the best athletes or not getting the best training as they are getting in other countries?

JAMES BLAKE: I don't think it is the training. I think it is the fact that there is a lot more competition in the States. There is basketball, there's football, there's baseball. Soccer has become more popular in the States. Lacrosse has become more popular.

So, some of the athletes are going to other sports.

JEFFREY BROWN: Former American great Jim Courier faced plenty of stiff competition from abroad while winning four Grand Slams in the early 1990s. Today, Courier serves as captain of the U.S. Davis Cup team, which competes with teams from other countries.

He says players around the world are better than ever, with access to all they need to reach the top.

JIM COURIER, Captain, U.S. Davis Cup: I think we have to understand that the world is very different than it was when Americans had nearly 50 percent of the top 100 players.

We had the best coaching systems. We had the best information. The world wasn't flat, to borrow Tom Friedman's book title. Information wasn't democratized amongst the Internet.

JEFFREY BROWN: As for American women, no one not named Williams has won a major championship since 2002. But a new generation has been on the rise. Washington Post tennis writer Ava Wallace.

AVA WALLACE, The Washington Post: On the women's side, there's a lot of optimism. There is people like Madison Keys and CoCo Vandeweghe, Sloane Stephens, who have all, I believe, made semifinals of Grand Slams, which is ultimately the goal in American tennis.

That's what the USTA has already said. They want to make Grand Slams, and they want to make the second week of Grand Slams.

JEFFREY BROWN: The USTA, the sport's governing body in this country, has been working hard in recent years to develop a new pipeline of talent among women and men.

For youngsters, there's a program called Net Generation. They were out in force at the U.S. Open watching the pros. For older players, there is a new centralized collaborative approach called Team USA, which offers support, including financial subsidies, to every American ranked in the top 500.

That effort got a huge boost this January with the opening of a $60 million 100-plus-court training center near Orlando, where juniors, collegiate players and pros can live and work part- to full-time and get a variety of help to supplement their own private coaching.

MARTIN BLACKMAN: Maybe it's strength and conditioning. Maybe it is mental skills. Maybe it's on-the-road coaching.

But there is a way that we can help. You're still preserving that customized team around the individual player, but, at the same time, you are leveraging the performance team expertise that they need to maximize their potential.

It is a model that has been used by a lot of Olympic sports.

JEFFREY BROWN: Last week, one American player mentored by Blackman, 19-year-old Frances Tiafoe, pushed Federer to the limit, before falling in five sets.

Taylor Fritz, also 19, won his first ever Grand Slam match here. After losing a tough second round match, he gamely talked with us about being part of the new USTA approach.

TAYLOR FRITZ, U.S. Tennis Professional: I kind of like the Team USA group. It is all the young American guys, we all train together, practice together. We root for each other. We all want each other to do the best, and we push each other.

There is like a good competitiveness amongst ourselves.

JEFFREY BROWN: American women on their way to the semifinals also spoke of the camaraderie they feel.

And there is more talent just behind them. Shelby Rogers, in the bright yellow shirt, seeded number 62 here, won one of the most thrilling matches, meeting the higher seeded Australian Daria Gavrilova in a U.S. Open women's record for length, three hours and 33 minutes. Afterwards, she was tired but happy.

SHELBY ROGERS, U.S. Tennis Professional: I love matches like that. You know, that is why I play the sport, the competing, the individuality, the fight.

JEFFREY BROWN: Rogers lost to the number four seed in her next match, but she is a big believer in the potential of her group of American women coming up after the Williams sisters.

SHELBY ROGERS: Venus is still killing it. I love it. But they have been great mentors for us as well. We genuinely want each other to do well, which is a really cool thing to be a part of.

JEFFREY BROWN: Will it work toward putting American men and women atop the tennis world over the long run? Before this week's string of success by American women, former champion Jim Courier said this:

JIM COURIER: We have to also realize that this is very much a meritocracy.

The thing that I preach to our young kids is, we are not entitled to success. Because we're American, it means nothing. The tennis ball has no idea what country you are from when you hit it. We have got to earn it like everyone else. We have got to be as hungry, if not hungrier, than everyone else. And we have got to go get it. So, that's my message.

JEFFREY BROWN: For the moment, plenty of reason for hope, particularly with the final foursome this weekend. So, keep your eye on the bouncing ball.

For the PBS NewsHour I'm Jeffrey Brown at the U.S. Open in Flushing Meadows, New York.