Venus Williams did her part to set up yet another Grand Slam family reunion, beating Agnieszka Radwanska 6-1, 6-3 Monday to reach the quarterfinals at the U.S. Open.

After she won, Williams could only wait to see whether she'd play her sister Wednesday in the next round. Serena Williams was set to face Severine Bremond on Monday night.

Both sisters are two-time U.S. Open champions. They are 8-8 overall against each other, including 5-5 at majors. Their matchups, however, usually come much later than the quarters.

"I mean, it's tough to play her because she's so good," Venus Williams said. "We're going stronger than ever, in my opinion."

Seeded seventh, she had it all over her 19-year-old opponent — experience, stature and height. At 6-foot-1, she gently leaned across the net to easily put away a floating return by the No. 9 Radwanska.

Top-seeded Rafael Nadal had a much tougher time. He withstood his first test at Flushing Meadows, shifting into another gear to beat Sam Querrey 6-2, 5-7, 7-6 (2), 6-3 and match his best result at the tournament that's always bedeviled him.

Playing for the sixth year at the U.S. Open, Nadal rallied to reach the quarterfinals. He got quite a workout — and a scare — from his unseeded, 20-year-old opponent.

"Very tough," Nadal said. "Sam is a big player, a big server. He has a great future."

Down 6-5 in the third set, Nadal suddenly flashed the form that won at Wimbledon, the French Open and the Olympics. Hitting harder, grunting louder and moving in closer, he quickly forced a tiebreaker and jumped to celebrate.

Nadal won the final four points to take the tiebreaker and later served out the match.

Ranked 55th, Querrey gave a solid show and became the first player to take a set from Nadal at this Open.

Crowds at Arthur Ashe Stadium love to root for underdogs, especially Americans. The fans in his private box were vocal, particularly the three who had their shirts off and spelled out S-A-M on their chests.

A bit jittery at the start, the 6-foot-6 Querrey boomed 20 aces and showed no fear, trading big shots with Nadal all match long. He drew a standing ovation at the end for his effort, and smiled broadly.

"Came up a little short. The guy's too good," Querrey said.

Nadal next plays unseeded Mardy Fish, who reached the quarterfinals at the U.S. Open for the first time with a 7-5, 6-2, 6-2 win over No. 32 Gael Monfils.

Playing in his ninth U.S. Open and coming off his upset over James Blake, Fish kept busy as his wedding approaches. He will marry "Deal or No Deal" model Stacey Gardner on Sept. 28 — she watched from his private box, minus her shiny No. 2 briefcase.

"I desperately wanted to play well here," he said. "Desperately."

Sixth-seeded Dinara Safina also made it into the quarters, beating Anna-Lena Groenefeld 7-5, 6-0. No. 16 Flavia Pennetta won, defeating No. 32 Amelie Mauresmo 6-3, 6-0.

Fish matched the best Grand Slam result of his career, having reached the quarters at the 2007 Australian Open. Ranked as high as No. 17 in 2004, the 26-year-old Fish has worked three years to recover from an injured wrist that required extensive surgery.

Fish waved to his private box after match point. The entourage included his father, Tom, who celebrated his birthday. No such fun for Monfils, who turned 22 Monday.

Safina coasted home after a close first set. She equaled her best result at Flushing Meadows, and kept up the best season of her career.

Safina reached the final at the French Open and later won 15 straight matches before losing to Elena Dementieva in the gold-medal match at the Olympics.