SERENA WILLIAMS celebrates her win over Britain’s Johanna Konta during their quarterfinal at the Australian Open tennis championships in Melbourne, Australia, on Wednesday.

SERENA WILLIAMS celebrates her win over Britain’s Johanna Konta during their quarterfinal at the Australian Open tennis championships in Melbourne, Australia, on Wednesday.

MELBOURNE, Australia

The last time Serena Williams and Mirjana Lucic-Baroni played each other, nearly two decades ago at Wimbledon, they were both precocious teenagers just starting their tennis careers.

Now, the two 30-something women will meet again in the semifinals of the Australian Open, a tournament that’s starting to have a distinct throwback feel.

Serena Williams, 35, reached her 10th consecutive Grand Slam semifinal with a 6-2, 6-3 win over Johanna Konta today, while Lucic-Baroni, 34, upset fifth-seeded Karolina Pliskova 6-4, 3-6, 6-4, to advance to her first major semifinal in nearly 18 years.

“Thirties is the new 10,” Williams said. “No matter what happens, someone 34 or older will be in the final.”

On the men’s side, 30-year-old Rafael Nadal dominated third-seeded Milos Raonic 6-4, 7-6 (7), 6-4 on Wednesday to join 35-year-old Roger Federer and 31- year-old Stan Wawrinka in the semifinals. It’s the first time since the 1968 French Open that three 30-somethings made the men’s semifinals at a Grand Slam.

Nadal will play Grigor Dimitrov, who beat David Goffin 6-3, 6-2, 6-4.

With 36-year-old Venus Williams also reaching the semifinals in the women’s draw, it’s also the first time in the Open era that two players aged 35 or older have reached the final four of a Grand Slam. Venus plays another American, CoCo Vandeweghe, in her semifinal on Thursday.

Serena Williams was tested by Konta in the second set when the British player broke her to go up 2-1. But Williams broke back at love to level the score at 3-all and saved another break point in her next service game before closing out the match.

Williams finished with 10 aces, but only connected on 45 percent of her first serves overall.

“The main focus is actually my serve,” said Williams, who is aiming for a record 23rd Grand Slam title. “I got a little frustrated, but then I just told myself, ‘Serena, stop complaining. Don’t be Baby Rena out here.’”

Lucic-Baroni advanced to the last four at a major for the first time since her run to the Wimbledon semifinals in 1999 at the age of 17. She is surprised she is getting another chance at this stage of her career.

“I know this means a lot to every player to reach the semifinals, but to me, this is just overwhelming,” she said, in tears, after the match. “This has truly made my life and everything bad that happened, it has made it OK.”

Lucic-Baroni was once considered a prodigy with as much promise as the Williams sisters. She won the first tournament she entered as a 15 year old in 1997 and several months later captured the 1998 Australian Open doubles title with Martina Hingis.

After Lucic-Baroni’s run at Wimbledon the following year, her career was sidetracked by personal issues and financial problems. She was largely out of the sport for several years before launching a comeback in the late 2000s.

Despite her recent difficulties, Lucic- Baroni said she never lost the belief she could compete at the top of the game.

“When you stop winning as much and you don’t play for a long time, yeah, you definitely lose it a little bit,” she said. “Not even lose it, you forget it. … And I’m really glad that I remembered.”

Nadal, whose ranking has slipped to No. 9, also believed he’d return to another Grand Slam semifinal despite struggling with injuries and a lack of confidence in recent years. The last time he made it this far was at the 2014 French Open when he claimed his 14th Grand Slam title.

The win over Raonic was Nadal’s 50th at Melbourne Park, where he won the title in 2009 and lost in the final in 2012 and ‘14. The Spaniard saved six set points in the second set, including two in the 13-minute tiebreaker.

Raonic, who aggravated an adductor injury during the match, had beaten Nadal in their most recent match two weeks ago in Brisbane.

“Even when I was winning a lot I had doubts, you can imagine I had more when I had injuries,” Nadal said. “I think I had a great career, but at the same time I had a lot of tough moments. That makes me enjoy even more the good moments I’m having today.”

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