NEW YORK, September 7- Serena Williams, chasing a calendar Grand Slam, advanced to a dramatic US Open quarter-final showdown with sister Venus on Sunday while a concussion forced Canada’s Eugenie Bouchard out of the tournament.
World number one Serena served well in moving within three match victories of a 2015 sweep of major titles by defeating US 19th seed Madison Keys 6-3, 6-3.
Serena, who struggled with her serve in two prior triumphs, hit 58 percent of her first serves and made only six unforced errors to 19 for Keys. She took 70 percent of points on her second serves, nearly twice Keys’ second-try effectiveness.
“My serve was definitely better. I also was hitting them a lot harder than I normally hit them,” Serena said. “My only chance was to start out fast. I just stayed in there and was able to relax.”
Venus, seeded 23rd, downed 152nd-ranked Estonian teen qualifier Anett Kontaveit 6-2, 6-1 at Arthur Ashe Stadium, matching her deepest Grand Slam run since reaching the 2010 US Open semi-finals.
“We’re both prepared,” Venus said. “Even though you’re playing your sister you have to be prepared and focus. The preparation doesn’t change.”
Serena, who holds all four major tennis titles, is trying to complete the first calendar Grand Slam since Steffi Graf in 1988 and match Graf’s Open Era record of 22 career Slam singles titles by capturing her Open Era record seventh US Open crown.
But Venus, two years older than Serena at 35, could play the spoiler as she tries to add to a trophy collection that includes the 2000 and 2001 US Opens and five Wimbledon titles, the most recent in 2008.
“I don’t think anyone wants to be a spoiler. I think people love to see history being made,” Venus said.
“But at the same time, you’re focused on winning your match even though the circumstances are really much different than you.”
Bouchard, who suffered a concussion after slipping in the locker room late Friday and hitting her head, pulled out of her match against Italy’s Roberta Vinci.
Bouchard had withdrawn from mixed and women’s doubles on Saturday.
The 21-year-old from Montreal was a French and Australian Open semi-finalist last year and lost the 2014 Wimbledon final to Petra Kvitova.
Her head injury added to a season of setbacks, including first-round French Open and Wimbledon exits and a 12-17 record.
Vinci advanced by walkover to her third US Open quarter-final in four years, matching her deepest Grand Slam run.
She next faces France’s Kristina Mladenovic, who eliminated 13th-seeded Russian left-hander Ekaterina Makarova, a semi-finalist at last year’s US Open and this year’s Australian Open, by 7-6 (7/2), 4-6, 6-1.
Mladenovic, on her deepest Grand Slam run, has never played Vinci.
Serena leads the Williams sibling rivalry 15-11 but they have split four US Open meetings, including the 2001 and 2002 finals, and Serena won their most recent matchup in round of 16 at Wimbledon in July.
Serena won her first set in 27 minutes, Keys handing her the lone break in the sixth game. Serena hit a backhand winner to break Keys for a 4-3 edge in set two and won when Keys, who also lost to Serena in the Australian Open semi-finals, double faulted to end matters after 68 minutes.
“She is playing great,” Serena said of Venus. “I have to play like I did today or better. But at least one of us, a Williams, will be in the semis, so that’s good.”
Venus, who lost the 1997 US Open final to Martina Hingis when Kontaveit was 21 months old, broke in the fourth game and and again in the eighth to grab the first set in 24 minutes.
Kontaveit, who lost in the first round at the past two Wimbledons in her only prior Grand Slam appearances, surrendered two breaks for a 4-0 hole in set two and Williams held twice more, denying the European’s lone break point in the final game to win in 50 minutes.
“Experience helped a lot,” Williams said. “I was able to understand what it’s like to play in this moment more than she was.”
Even with the loss, 19-year-old Kontaveit will nearly double her career prize money with $213,575 for her US Open run.