In other news, Muguruza reaches Stanford semis and Halep retires in Washington.
Federer to play in first match since Wimbledon title win in Canada next week
Roger Federer will play his first match since winning his 19th grand slam title last month at Wimbledon next Wednesday at Montreal, ATP Rogers Cup organisers said on Friday.
Federer, 35, Swiss has a first-round bye in the Canadian hard-court event, his first tune up for the US Open, which begins August 28 in New York.
Federer's first foe since claiming his eighth Wimbledon crown will be the winner of a first-round match between Canadians Vasek Pospisil and Peter Polansky, according to the draw made on Friday.
For the first time since 2011 in Monte Carlo, top-ranked French Open winner Rafael Nadal and second-ranked Federer, who also won this year's Australian Open, find themselves at opposite ends of a draw as top seeds.
Nadal's first match will be against either Croatian Borna Coric or a qualifier.
Victorious Muguruza pleased with accuracy
Wimbledon champion Garbine Muguruza swept into the semi-finals of the WTA hard-court tournament at Stanford on Friday with a 6-1, 6-3 win over Ana Konjuh.
Spanish top seed Muguruza needed just 62 minutes to get past the fifth-seeded Croatian, breaking Konjuh's serve five times and never trailing in their first career meeting.
"I think today I was very accurate," said Muguruza, the world No 4 who is playing her first tournament since beating American Venus Williams in the final at Wimbledon.
That gave Muguruza a second grand slam title to go with her 2016 French Open crown.
"Ana is such a powerful player and super-young," Muguruza said. "I knew I had to be concentrated. I'm super happy that I'm through to the semi-finals, and I'm pretty happy with the match."
Muguruza, who is seeking her second title of 2017, next faces American Madison Keys, who beat seventh-seeded Lesia Tsurenko of Ukraine 6-4, 6-3.
"She started off the match well," Keys said. "I wasn't overly stressed about it, I knew I could get myself out of that hole.
"I'm feeling really good and happy to be out on the court, playing multiple matches. I haven't had many matches, so I feel like I'm still trying to find that rhythm again."
Eighth-seeded American teenager CiCi Bellis surprised two-time Wimbledon champ Petra Kvitova 6-2, 6-0.
Bellis, 18, moved the Czech all around the court, dropping just two games in the one-hour match.
Bellis will square off against sixth-seeded American CoCo Vandeweghe in the semis. Vandeweghe rolled over fourth-seeded Russian Anastasia Pavlyuchenkova 6-2, 6-3.
Heat forces Halep to retire in Washington
Ekaterina Makarova reached the Citi Open semi-finals when Simona Halep retired in the third set of their match in Washington.
Heat illness was apparently the reason for the top seeded Romanian's retirement shortly after she lost the second set of the quarter-final at Rock Creek Park Tennis Center.
The Russian's 2-6, 6-3, 1-0 success means she will face Oceane Dodin for a place in the final, after the Frenchwoman's 5-7, 6-4, 7-6 defeat of Germany's Sabine Lisicki.
The other semi-final is an all-German affair. Julia Goerges beat Romania's Monica Niculescu 6-3, 6-4 to set up a match against Andrea Petkovic, who beat Canada's Bianca Andreescu 6-7, 6-1, 6-2.