American Taylor Fritz shocked world number one Carlos Alcaraz 6-3, 6-2 as Team World won all three singles matches at the Laver Cup on Saturday to power into the lead in the global tennis event.
Fritz, ranked fifth in the world, notched his first victory over the Spanish superstar after three previous defeats, including in the semi-finals at Wimbledon this year.
Added to victories for Australian Alex De Minaur and Argentina's Francisco Cerundolo, it gave captain Andre Agassi's team a 7-3 lead over Team Europe with the night's doubles still to come.
The first team to 13 points will lift the cup on Sunday.
Two weeks after beating Italian Jannik Sinner in the US Open final to claim a sixth Grand Slam crown and return to number one, Alcaraz was not at his sharpest.
Fritz took full advantage with an aggressive game, breaking Alcaraz once in the first set and twice in the second and saving both break points he faced.
"I knew what I had to do before I came out here tonight, the question was just if I was going to be able to do it," Fritz said.
"I didn't second guess myself, didn't play too safe. I played with no fear on the big points."
Agassi was an energetic observer and adviser on the sideline at Chase Center, home of the NBA's Golden State Warriors.
Warriors superstar Stephen Curry got a warm reception when he officiated at the coin toss -- assisted by retired Swiss tennis great and Laver Cup co-creator Roger Federer -- before the Alcaraz-Fritz match.
Team World had trailed 3-1 after the opening day.
But with victories worth two points on Saturday, Team World pulled level on Australian De Minaur's 6-1, 6-4 win over world number three Alexander Zverev of Germany.
Argentina's Cerundolo then outlasted Denmark's Holger Rune 6-3, 7-6 (7/5).
World number eight De Minaur, a late replacement for the injured Frances Tiafoe, raced through the opening set and held firm as third-ranked Zverev kept it close in the second.
"I knew it was only going to get harder," said De Minaur, who claimed just his third victory over Zverev in 11 encounters.
All three of those wins have come in team events, two at the ATP Cup and one at the United Cup.
"I think it brings a different type of energy," De Minaur said. "I enjoy when there's a bench, teammates I'm playing for."
De Minaur used his speed and a deft touch at the net, saying he needed to employ a wide variety of shots on the unusually slow Laver Cup surface.
De Minaur even channeled Federer, who was in the stands, with an effective backhand slice.
"He wrote the playbook, I just read it," De Minaur said.