MELBOURNE, Australia — Emma Raducanu wasted no time in announcing her presence in her first Grand Slam match since her stunning run to last year’s U.S. Open title.

After hitting a forehand winner down the line past Sloane Stephens — the 2017 U.S. Open champion — Raducanu shouted a loud “Come on,” punctuating the first point of the match.

From there, Raducanu was off and running, sprinting through the first set in 17 minutes with the loss of just four points. Though Stephens found her footing in the second set and was able to prolong rallies with her foot speed and counterpunching, Raducanu regained control in the final frame to close out the match 6-0, 2-6, 6-1 on Tuesday night in Margaret Court Arena.

When a backhand half-volley from Stephens hit the net to end the match, Raducanu dropped her racket and covered her face with her hands, a reaction rarely seen from a top player after a first-round win. Then again, rarely has a player reached the top after having skipped so many rungs on the ladder. Seeded 17th, this is Raducanu’s first appearance in the women’s competition at the Australian Open, and only her third Grand Slam event over all. During last year’s Australian Open, Raducanu was ranked 348th, opting to stay home and study for high school exams rather than traveling to Australia.

Tuesday’s match, only the second night match of Raducanu’s career, was also the first time she had played a third set at a Grand Slam: Her run to the U.S. Open title last year, which began in qualifying, entailed winning 20 straight sets across her 10 matches.

“I think 2022 is all about learning for me,” Raducanu said. “Being in those situations — winning a set and then having to fight in a decider — is definitely all just accumulating into a bank of experience that I can tap into later on down the line. Yeah, very happy that today I can add to that.”

Despite being a Grand Slam champion herself, Raducanu had never faced one before Stephens.

“When Sloane was fighting back in the second set, I definitely accepted that,” Raducanu said. “I was almost expecting it, because she is a champion and you don’t just become one by rolling over.”

Raducanu will play her second-round match on Thursday against the Montenegrin Danka Kovinic, another early steppingstone for a player who has already shot to superstardom in her home country. Raducanu’s U.S. Open win propelled her to the BBC’s Sports Personality of the Year award, and she was named an M.B.E. — Member of the Most Excellent Order of the British Empire — on the Queen’s New Year’s honors list. Shortly after her triumph in New York, a congratulatory message to Raducanu appeared on the Royal Mail’s postmarked envelopes across Britain for four days.

Stephens, 28, admitted that while both she and Raducanu had won in Flushing Meadows, their titles had little in common. “We won the U.S. Open, but our situations are very different,” Stephens said. “I think she is carrying a whole country, and that’s quite different than my win at the U.S. Open.”

Despite her swift success, Raducanu has received blowback from members of the British media, who have suggested that she has not focused enough on her tennis after her results dipped following a windfall of endorsements. In Nike’s first video advertisement featuring the 19-year-old, the company dramatized those criticisms, showing Raducanu playing as phrases like “fluke” and “one-hit wonder” flashed behind her in capital letters.

For those who had wanted to make uncharitable assessments, there had been some reason for concern: Raducanu had lost four of the six matches she had played since winning the U.S. Open, including a brutal 6-0, 6-1 loss to Elena Rybakina last week in Sydney.

Raducanu, whose training before the match in Sydney had been limited by a recent case of the coronavirus, said she was “very happy to have turned it around so quickly” after that stark defeat.

“The last week I put some great work in,” she said. “Sydney for me, wasn’t a deal breaker. I was still feeling positive; I just knew where I was at that point.”

Stephens, who noted the “massive scream” Raducanu let out after the first point of the match, said that she could sense Raducanu’s readiness to silence doubters.

“I think the hardest part is trying to prove that you are good enough to be where you are or good enough to stay where you are,” Stephens said. “The more you try to do that, I think, the more emotion shows and the more things are probably out of character than normally you would do, because you’re trying so hard to show and prove that you’re this person, or this ranking.”

Raducanu said she also has had to learn to deal with self-criticism.

“The biggest challenge is to be patient,” Raducanu said in her pretournament news conference. “I’m a bit of a perfectionist. Whether that’s practice, whether that’s off the court, I want to be the best I can all the time; sometimes it’s just not very viable.”

She added: “I need to just relax. As long as the trend is trending upward, just a matter of small fluctuations, I think I can be proud. Whatever challenge that is, I feel kind of ready to face it now.”

While Raducanu’s career continues to trend upward, Stephens said that her accomplishments have come in a “very backward” sequence.

“It’s hard to manage,” Stephens said of Raducanu’s uncharted trajectory. “But I think if you have the right people in your corner guiding you, they will know when to take breaks. They will know when to push her harder, and they will know when she’s up for it.”

Stephens had been expecting to be on a break of her own during this tournament. She married her longtime boyfriend, the soccer player Jozy Altidore, on New Year’s Day, and said she planned the wedding for January because she had “fully planned on skipping” the Australian part of this season. She said she had not wanted to take the risk of having to quarantine and of having to retread upon the pain she felt here a year ago: While enduring the mandatory hotel quarantine before last year’s Australian Open, Stephens attended the funerals of her grandparents via Zoom.

“Last year, I had a very traumatizing experience in quarantine, and I just wanted to completely remove myself from that,” Stephens said on Tuesday. “No matter what, even if it was like two days, I didn’t want to do it.”

Stephens, who said she had completed full-fledged off-season training, said people close to her were caught off guard when she decided to make the unexpected trip Down Under.

“I think everyone was a little bit surprised,” she said. “But, yeah, I just was like: ‘I’m ready.’”

Her opponent, Raducanu, proved that she was even more ready.