Kerber, who just turned 30, is back on a high in Melbourne: reading the flow of play beautifully, bending low and slapping straight-line winners off ill-considered shots from her opponents.

Even on a very good day for Keys, beating this version of Kerber would have been difficult. But on another tough day for Keys in the Grand Slam spotlight, this match quickly turned into a mismatch.

It was 4-0 Kerber in 14 minutes, 6-1 Kerber in 22 minutes. And, ultimately, despite all of Keys’ ball-striking talent and earnest offseason efforts, it was 6-1, 6-2, Kerber, in 51 minutes.

“I was just playing my game, not thinking a lot about winners or errors, just trying to stay in the moment and play every single point,” said Kerber, who will next face the winner of Wednesday’s later match between Simona Halep and Karolina Pliskova. The other semifinal in the women’s draw will feature Elise Mertens, an unseeded Belgian, and Caroline Wozniacki, the No. 2 seed from Denmark.

Kerber’s expeditious victory over Keys will only boost her already soaring confidence, and will also leave her as fresh as possible for her semifinal match on Thursday.

On Wednesday she looked ready to run and run, even if she joked after the match that, as a newly minted 30-year-old, she needed to shorten her rallies.

“I am getting so old, so I have to be aggressive,” said Kerber, the No. 21 seed from Germany. “I cannot run for every ball anymore. I have to change something.”

She actually has changed plenty for 2018, splitting with her longtime coach Torben Beltz and hiring Wim Fissette, a veteran Belgian coach who has been a huge influence on other champions in the past, including Kim Clijsters, Victoria Azarenka and Halep.

Fissette does not tend to stay in his posts for long, but he is clearly an excellent analyst.

“She had great success with Torben but sometimes you need to change, just to hear a different voice,” said Barbara Rittner, the German Fed Cup captain. “It’s not a matter of the coach is bad or the player is bad. You just need to hear something new to respond better and try new things.

“Wim is a positive guy. He has a game plan, and he knows what he’s doing.”

The effects have been immediate. After winning four matches at the exhibition Hopman Cup team event in Perth, Australia, Kerber has won 10 straight official matches to start the season.

After winning the Australian Open and U.S. Open in her breakthrough 2016 season, she struggled for much of 2017. But Wednesday’s victory guaranteed that she would return to the top 10 after this tournament.

“So many things happened to her, both good and bad, in the last 24 months,” Rittner said. “We talked about it in Luxembourg at the end of the year. It really was a lot to absorb, and she is someone who is thinking about things quite a lot, not just taking it lightly and going her way. It took her a while just to settle down and find herself again — having fun and being focused. And for the moment she is not looking back or looking forward.”

Facing Kerber did not look like much fun for Keys on Wednesday. Keys is hardly the only big hitter with limited defensive skills to suffer here at Kerber’s deft hands. She also routed Maria Sharapova, 6-1, 6-3, in the third round in 64 minutes before nearly falling against the stylistic outlier Hsieh Su-Wei in the fourth round, finally prevailing in three sets.

But Sharapova, despite the lopsided score, looked fully engaged in the combat from start to finish. Keys, despite some glimpses of her big-hitting potential, appeared edgy and restricted, much as she did in last year’s U.S. Open final against Sloane Stephens, when Keys also won just three games.

“I think she played really well,” Keys, the No. 17 seed, said of Kerber. “I felt like I was trying different things, but I wasn’t playing very consistent. I think in the first set I played really passive, and because of that I feel like I wasn’t moving as well, wasn’t accelerating.

“So I wasn’t very happy with how I played today, but still, I was fighting and trying to stay in the match. Sometimes you just don’t play very well out there.”

But Keys said she believed she and her coach, Lindsay Davenport, formerly an intimidating baseline player who won three major singles titles, are on the right track.

“I feel that,” Keys said. “I think how I played all of the other matches definitely shows that, and I’m not going to walk away from this tournament and think it was terrible because I had one bad match. I definitely think I have taken a lot of steps in the right direction and feel good about my game and feel like I’m thinking a lot clearer out there. I think it’s just going to take a little bit of time.”

In earlier years, a defeat like Wednesday’s might have left her tight-lipped and emotional, but Keys was expansive and dry-eyed in her post-match news conference.

“I’m evolving guys,” she said, smiling. “I’m growing.”

Keys can be extremely tough when she is serving big and swinging with confidence, as she showed against Caroline Garcia, the rising French star, in the fourth round here.

But she could not find a way to do justice to her abilities on Wednesday, making nearly twice as many unforced errors as winners and often rushing when patience would have been advisable.

Kerber is a tough matchup for Keys even on a good day. She has now lost seven of her eight matches against the counterpunching German, the last four in straight sets.

This was far, far from a good day.

This article originally appeared in The New York Times.