Time to make room for gold No. 19.

With yet another dazzling performance, the most decorated athlete in Olympic history added to his staggering haul Sunday night in the 4x100-meter freestyle relay, giving the United States a lead it never relinquished.

"When I was on the block, I honestly thought my heart was going to explode out of my chest," Phelpssaid. "I was so hyped tonight and so excited."

Defending Olympic champion France was out front when Phelps dove into the water on the second leg, taking over for leadoff swimmer Caeleb Dressel. Even though the 100 free isn't one of Phelps' specialties - he's never swam it individually at the Olympics, only in the relays - he blazed down and back in a stunning 47.12 seconds, a time that was faster than all but the three anchors on the medal-winning teams, three of the best in the world at that distance.

"Coming off the wall I thought my kickout was great," Phelps said. "I just wanted to hammer it, hit the touch and give them a bigger lead."

That he did.

Ryan Held kept the Americans in front before giving way to Nathan Adrian, the nation's best sprinter.

At that point, it wasn't really in doubt.

But Phelps wasn't taking any chances, pounding the starting block and shouting toward Adrian as the anchor made the turn for home.

When Adrian touched the wall first in 3 minutes, 9.92 seconds, Phelps thrust his right arm in the air and looked toward his infant son Boomer, nuzzling in the arms of his mother Nicole Johnson, the roaring crowd blocked out by noise-canceling headphones.

Little Boomer won't remember what his daddy did this night.

But that gold medal will never let him forget.

It was quite a night for the Americans, who were shut out on the golds on the opening night of swimming.

Racing nothing but the clock, Katie Ledecky gave the U.S. its first victory by crushing her own world record in the 400 freestyle.

The result was totally expected. The unassuming teenager from suburban Washington has dominated the longer freestyle events since winning gold in the 800 free at the London Olympics as a 15-year-old.

The only drama was whether she'd take the world record even lower.

Her powerful stroke quickly made that a moot point, too.

Ledecky kicked off the first wall with a lead of nearly a body length and steadily pulled away from the overmatched field - as well as the world-record line superimposed on the video screen.

Her arms churning effortlessly through the water, Ledecky touched nearly 5 seconds ahead of her closest pursuer and quickly whipped around to look at the scoreboard.

When Ledecky saw the time - 3:56.46 - she let out an uncharacteristic scream and shook her right fist. She crushed the mark of 3:58.37 that she set nearly two years ago on the Gold Coast of Australia, and had been chasing ever since.

"I was pumped," Ledecky said. "That's what I wanted and I had been so close to breaking that all year, the past two years. I knew I was due for a breakthrough."

She's just getting warmed up.

Ledecky, who added gold to the silver she won in the women's 4x100 free relay, is also favored in other two individual events: the 200 and 800 free. She could pick up another gold in the 4x200 free relay.

It was a night of world records in Rio.

Britain's Adam Peaty set his second mark in as many nights in the 100 breaststroke, while Sarah Sjostrom of Sweden eclipsed her own mark in the 100 butterfly.

In all, six world records have fallen on the first two days of swimming.

The whipping gusts that disrupted athletes and spectators alike were just a prelude to the winds of change that roared through Rio de Janeiro on Sunday night: Serena and Venus Williams lost an Olympic doubles match for the first time.

Day two of the Rio Games proved quite the breeze for some athletes and much too windy for others. The gusts ripped apart a large decorative panel on the swimming venue and even shut down shopping at the megastore - essentially an enormous tent - inside the Olympic Park.

Novak Djokovic shook his head and placed his palm over welling eyes on his way to the locker room after a first-round Olympic exit, devastated he might never realize his goal of adding a gold in singles to a substantial collection of Grand Slam titles.

"I mean, no doubt, it's one of the toughest losses in my life, in my career," Djokovic said later, shaking his head and speaking in subdued tones. "Not easy to handle."

The Serb was hardly alone in his disappointment on Day 2 of the Rio de Janeiro Games: He was one of three No. 1 seeds to exit the tennis competition in a wild span of 12 hours.

Djokovic 7-6 (4), 7-6 (2) setback Sunday night was caused in large part by ferocious forehand after ferocious forehand from a resurgent Juan Martin del Potro of Argentina. That surprising result followed losses by the top-seeded duos of Serena and Venus Williams of the United States — who entered their match with a 15-0 Olympic record and three gold medals as a pair — in women's doubles, and Nicolas Mahut and Pierre-Hugues Herbert of France in men's doubles.

China won yet another medal in air rifle on a day nasty winds sent the clay targets in the trap event bobbing and bouncing through the air, forced delays on the tennis courts and whipped up treacherous waves in the Rodrigo de Freitas Lagoon.

Sunday's rowing regatta was called off after a two-hour delay when the choppy seas didn't let up. Race officials said winds gusting up to 34 mph (15 meters per second) pushed buoys into the lanes and capsized two boats during morning practice.

The Americans had another shattering disappointment in the women's road race when three cyclists blew past Mara Abbott within sight of the finish line. Dutch rider Anna van der Breggen led the charge, giving the Netherlands back-to-back golds in the event.

Her teammate Annemiek van Vleuten crashed while leading the race on the same final decent where Giro d' Italia winner Vincenzo Nibali and Colombian climber Sergio Henao tumbled while leading the men's race Saturday. Van Vleuten sustained three small fractures in her spine and was hospitalized in intensive care.

Other highlights from Day 2 of the Rio Games:

Diana Taurasi and the U.S. women's basketball team opened their Olympics with a record rout, smashing Senegal 121-56 while setting Olympic marks for most points in a game, margin of victory and assists (36). The Americans, also featuring first-time Olympians Brittney Griner, Ella Delle Donne and Breanna Stewart, have won 42 consecutive Olympic games.

Majlinda Kelmendi won Kosovo's first Olympic medal, taking gold in the women's 52-kilogram judo division. The top-ranked Kelmendi struggled for years to represent her country, which declared independence from Serbia in 2008. At the last Olympics she represented Albania because Kosovo was not recognized by the International Olympic Committee until 2014.

China's bid for a gold in shooting seemed to take a hit when a two-time defending gold medalist failed to qualify. But Zhang Mengxue picked up the slack, earning China's fourth air pistol gold in the last five Games. China has dominated the air rifle and pistol shooting events at the Olympics, earning nine gold medals since the 2000 Sydney Games.

A day after gruesomely breaking his left leg while vaulting during men's preliminaries, French gymnast Samir Air Said posted a Facebook video from his hospital bed on Sunday thanking people for their support and pledging to shoot for Tokyo in 2020. Said underwent surgery to repair his fibula and tibia he fractured while trying to land a vault.