NEW YORK (AP) — No need for any extra practice for Serena Williams after this performance.

Plus, it’s not as if she needs to study too hard to figure out how to deal with her next opponent.

Playing far better than she did earlier in the U.S. Open as she chases a calendar-year Grand Slam, Williams set up a quarterfinal against older sister Venus with a 6-3, 6-3 victory over 19th-seeded Madison Keys on Sunday.

“A Williams will be in the semis, so that’s good,” the No. 1-seeded Serena said after needing only 68 minutes to dismiss Keys, a 20-year-old American with formidable serves and forehands who simply was outplayed.

Already a winner of the past four major tournaments, including last year’s U.S. Open, Serena is trying to become the first tennis player to win all four Grand Slam titles in the same season since Steffi Graf in 1988.

Venus, at 35 the oldest woman to enter the field, was on court even less time than her sibling, overwhelming 19-year-old qualifier Anett Kontaveit of Estonia 6-2, 6-1.

Venus’ match came first in Arthur Ashe Stadium, so then she had to decide whether to watch Serena play.

“I get very nervous, because even if I have to play Serena, I still want her to win, so I have a hard time watching unless she’s winning. Then it’s easy to watch,” said Venus, who won U.S. Open titles in 2000 and 2001, but had lost in the third round or earlier each of the past four years. “So it depends on how my nerves are.”