LONDON (AP) — Serena Williams watched her opponent's shot land beyond the baseline on match point.

She did not let out a shout, pump a fist or even crack a smile. This was no time to celebrate — not with older sister Venus at the other end of the court.

Serena trudged slowly to the net after her 6-4, 6-3 fourth-round win on Centre Court, and the two siblings shared a warm embrace at the end of their latest all-Williams matchup.

"It's hard to feel excited about (beating) someone you root for all the time no matter what and who you love so much and she's your best friend in the world," Serena said. "It's never easy but you just play for the competition and enjoy the moment."

In the 26th career meeting between the siblings, Serena dominated with her steady serve and big hitting from the back of the court, extending her Grand Slam winning streak to 25 matches.

The win sent the top-ranked Serena into the Wimbledon quarterfinals as she bids for a fourth straight Grand Slam title, a feat last accomplished by the younger Williams in 2003.

If Serena can triumph again, only the U.S. Open would stand in her way of becoming the first player to complete a calendar-year Grand Slam — a sweep of all four majors in the same season — since Steffi Graf in 1988.

"Sometimes you have to play people that you don't want to play," Serena said. "That happens. But overall I just enjoy it. "

Among others advancing Monday was 2013 men's champion Andy Murray, who beat 6-foot-11 Ivo Karlovic 7-6 (7), 6-4, 5-7, 6-4 to reach the Wimbledon quarterfinals for the eighth consecutive year. Karlovic served 29 aces but Murray broke twice and had only nine unforced errors.

Defending champion Novak Djovic and seven-time winner Roger Federer played late matches on "Manic Monday" — with all 16 men's and women's fourth-round matches on the schedule.

Both Williams sisters have won Wimbledon five times, but Serena also has a total of 20 Grand Slam titles. Another Wimbledon title will put her just one behind Graf, who holds the Open era record with 22.

Serena broke twice in each set and lost serve just once. She had 10 aces, as well as 36 winners and 13 unforced errors.

Monday's victory improved her career record against Venus to 15-11, including six out of their last seven matches, 8-5 in Grand Slams and 4-2 at Wimbledon. This was the sisters' first meeting at a major since the 2009 Wimbledon final, which was won by Serena.

Venus Williams, playing in her 18th Wimbledon, was the oldest woman in the draw at 35.

This was the earliest all-Williams match in a Slam since they met in the fourth round at the 2005 U.S. Open. Venus was asked whether it felt different playing her sister at such an early stage.

"It's definitely anticlimactic if this isn't a semifinal or a final," she said. "It's different. Especially when she's going for something this historic, which is achievable for her."

Serena will next face another familiar opponent — Victoria Azarenka, the two-time Australian Open champion from Belarus. Azarenka beat 18-year-old Belinda Bencic of Switzerland 6-2, 6-3.

Williams holds a 16-3 career advantage against Azarenka, including a 9-0 record in Grand Slam matches.

Serena was one of three American women to reach the Wimbledon quarterfinals Monday, along with CoCo Vandeweghe and Madison Keys. It's the first time that's happened since 2004 when Jennifer Capriati, Lindsay Davenport and Serena made it to the final eight.

The other women's quarterfinal matchups were set: 2004 champion Maria Sharapova against 47th-ranked Vandeweghe, Keys against Agnieszka Radwanska, and No. 15 Timea Bacsinszky against Monica Niculescu.

Vandeweghe surprised French Open runner-up and sixth-seeded Lucie Safavora 7-6 (1), 7-6 (4). Vandeweghe had never gone past the third round of any major until this year's Wimbledon.

Sharapova downed Zarina Diyas of Kazakhstan 6-4, 6-4. Sharapova has not dropped a set so far, losing only 23 games in four matches.

The 20-year-old Keys got to the Wimbledon quarterfinals for the first time, beating 122nd-ranked Olga Govortsova of Belarus 3-6, 6-4, 6-1.

Richard Gasquet held off 20-year-old Australian Nick Kyrgios 7-5, 6-1, 6-7 (7) 7-6 (6) to advance to the Wimbledon quarterfinals for the first time since making it to the semifinals in 2007.

Gasquet will now face Stan Wawrinka, who hasn't dropped a set all tournament. The fourth-seeded Swiss beat Belgium's David Goffin 7-6 (3), 7-6 (7), 6-4.

Vasek Pospisil rallied from two sets down to overcome No. 22 Viktor Troicki 4-6, 6-7 (4), 6-4, 6-3, 6-3. Pospisil — the third Canadian man to reach the quarterfinals at Wimbledon, after Robert Powell (1908, '10, '12) and Milos Raonic (2014) — will play Murray next.