Williams sisters to meet as Bouchard pulls out

First up on the Arthur Ashe Stadium Court, elder sister Venus wasted little time in beating 152nd-ranked Estonian teen qualifier Anett Kontaveit 6-2 6-1 in a one-sided encounter, taking less than an hour.

Later, top seed and grand slam seeking Serena dispatched fellow American and 19th seed Madison Keys, winning 6-3 6-3 with a single break of service in each set.

It kept her on course for the calendar grand slam, last achieved by Steffi Graf in 1988.

If she lifts the title Serena would also draw level with the German on 22 grand slam singles titles.

But first she must get past her sister Venus, who has found a new lease of life at 35, having not progressed so far in a grand slam since reaching the semifinals of the U.S Open in 2010.

They will battle for a semifinal place Tuesday, with Serena leading 15-11 in career meetings, most recently winning in the fourth round on the way to the Wimbledon title in July.

But at the U.S. Open their four meetings have been shared, including the 2001 final won by Venus, one of her seven grand slam titles.

Both were full of praise for their respective sibling after their wins.

"I'm so proud of Serena and I think she's proud of me. We inspire each other," said Venus.

"She is playing great," was Serena verdict on 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."

Bouchard pulls out

Their match up will be eagerly awaited, but there was disappointment for the New York fans Sunday as Canada's Eugenie Bouchard withdrew from the U.S. Open after failing to recovery from a head injury sustained in a freak locker room fall.

"Eugenie Bouchard is withdrawing from the women's singles competition at the 2015 U.S. Open due to a concussion," said a statement.

The 21-year-old had been due to face Italy's Roberta Vinci for a spot in the last eight.

Bouchard, returning to form after a dismal year, was also in the women's doubles and mixed doubles but has also been forced to pull out of those competitions.

Cilic marches on

In the men's singles, Marin Cilic continued his impressive defense of his title with a 6-3 2-6 7-6 6-1 win over France's Jeremy Chardy, shrugging off an ankle injury as he dropped the second set.

It is the 11th straight win at Flushing Meadows for the ninth seeded Croat, firing four aces to win a pivotal third set tiebreaker.

He will next meet Frenchman Jo-Wilfried Tsonga as the Frenchman eased past compatriot Benoit Paire in straight sets to earn his place in the quarterfinals.

(CNN)