Second seed Roger Federer defied a windy condition to sail into the last 8 of the US Open on Tuesday, as 10th seed Caroline Wozniacki dominated Sara Errani en route to her first Grand Slam semi-final in three years in the bottom half of the women’s draw.
Earlier, Peng Shuai became the third Chinese to make a Grand Slam last 4 after a comfortable win over rising start Belinda Bencic.
Frenchman Gael Monfils reached his second US Open quarter-final since 2010 with a roaring win over the youngest player in the men’s Top 10 ranking Grigor Dmitrov.
Monfil’s compatriot Gael Simons lost a four-setter to Coatia’s Marin Cilic and Tomas Berdych proved a handful for the only unseeded left, Thomas Thiem, 20.
Roger Federer (SUI)  beat Roberto Bautista Agut (ESP)  6-4 6-3 6-2
Swiss Federer showed some class on his way to a 6-4 6-3 6-2 win over one of the most improved player this season Agut to improve his own record at night matches in Arthur Ashe to 24-1.
The win saw the five-time champion tie Pete Sampras and Bill Tilden for 5th place, as the only players to have won 71 US Open singles matches.
Federer takes on No. 20 seed Monfils, who earlier on Tuesday reached his second Grand Slam quarter-final of the season with a straight-set win over Dmitrov.
Caroline Woznizcki (Den)  beat Sara Errani (Ita)  6-0 6-1
Dane Wozniacki made a work of her quarter-final contest with Errani 6-0 6-1 to reach her career fifth Grand Slam semis (her fourth at the US Open), still in Tuesday night’s windy atmosphere at the Arthur Ashe.
The 24-year-old only dropped serve in the opening game of the second set but stopped at not even a game to close out the match in 65 minutes.
It was not all gloomy for Errani, who hit 12 winners and 13 unforced errors, but Wozniacki was in a league of her own, blasting 26 winners to just 10 unforced errors.
“I always go out there and believe I’m going to play well, and I had a game plan in mind,” said Wozniacki, who produced 12 backhand winners to just 4 unforced on the night.
“I went for my shots. I knew I had to be aggressive but not too aggressive, kind of find a balance between finding the opening, then really going for my shots whenever I had the opportunity for it.”
“I have played so well here in the past. It’s tricky sometimes with the wind, but I know how to adapt and it’s been working out well so far.”
Awaiting Wozniacki in the last four is China’s Shuai, who has already proved her mettle against a number of seeds to reach the this round.
“It’s definitely going to be a different match than against Sara today… Peng is closer to the baseline and going for her shots more. It’s going to be a hard one, but it’s going to be fun,” she added.
Gael Monfils (FRA)  beat Grigor Dimitrov (BUL)  7-5 7-6(6) 7-5
Monfils, 28, overcame Dmitrov 7-5 7-6(6) 7-5 to claim their fourth round tie.
The Frenchman is yet to drop a set on his track through to the quarter-finals, after victories over Jared Donaldson, Alejandro Gonzalez and 12th seed Richard Gasquet.
The win over world No. 8 is his third over a player in the Top 10 this year and the 25th of his career.
Monfils was made to dig deep by the Bulgarian in the second and third sets, notably letting a 4-2 lead slip in the penultimate to save two set points in the resultant tie break and six of the seven break points he faced to close it out.
Peng Shuai (Chi) beat Belinda Bencic 6-2 6-1
Rave of the 2014 US Open women’s singles, Peng, claimed her first meeting with Bencic 6-2 6-1 in 64 minutes.
She hit 24 winners (including five aces) to just seven unforced errors, while an erratic Bencic came up with a less impressive 19 unforced errors to just 12 winners.
“It’s an amazing tome for me,” Peng said. “I love tennis and love to play, and it’s tough sometimes when I’m thinking of giving up and almost stopping playing because I don’t know if I can make it or not, but my coach and parents make sure I keep fighting and never give up.”
The win marked the sixth-longest wait for a first Grand Slam semi-final in the Open era. Pen follows Li Na (six-timer), Zheng Jie (twice) to become the third Chinese in the last four of a major.
Marin Cilic (CRO)  beat Gilles Simon (FRA)  5-7 7-6(3) 6-4 3-6 6-3
Top Croat Cilic avoided another five-set slip after his second round ouster at the hand of No. 26 seed Simons in the Aussie Open in January.
The 14th seed outlasted Simons 5-7 7-6(3) 6-4 3-6 6-3 to clinch his second last 8 ticket this season after Wimbledon- his first win in five meetings with his French opponent.
Tomas Berdych (CZE)  beat Dominic Thiem (AUT) 6-1 6-2 6-4
Berdych progressed to his 11th Grand Slam quarter-final with a 6-1 6-2 6-4 win over 45th-ranked Austrian Thiem.
Thiem, who turned 21 today, was bidding to become the first Austrian since Jurgen Melzer to reach the last 8 of a major, but came up against huge resistance in Berdych, who improved his record to 1-5 in fourth round matches in Flushing Meadows.