Daniil Medvedev was 7 years old and living with his family in Moscow when Roger Federer rose to No. 1 in the ATP rankings on Feb. 2, 2004.

There was no suspecting it then, but Federer’s achievement was the start of an extraordinary period of tennis domination by a small group of men who came to be known as the Big Four.

Together, Federer, Rafael Nadal, Novak Djokovic and, to a lesser degree, Andy Murray hoarded the Grand Slam singles titles and the regular tour’s most prestigious titles, taking turns at No. 1 for more than 18 years.

On Monday, Medvedev, a lanky 26-year-old Russian with a technique that is far from orthodox, will finally put an end to the Big Four’s numerical dominance, displacing Djokovic at No. 1.

“These guys have been amazing,” said Paul Annacone, the veteran coach and Tennis Channel analyst who once coached Federer.

Medvedev’s timing on the court is amazing, too: It creates wonderment at how someone whose long limbs seem to be flying in such contradictory directions can make such clean contact again and again.

But his timing in reaching No. 1 is not nearly so close to perfection.

Nadal, not Medvedev, is the ATP’s hottest player: resurgent at age 35 and 15-0 in 2022 after rallying to defeat Medvedev in a classic five-set Australian Open final and then defeating him again last week in much more straightforward fashion on his way to another title in Acapulco, Mexico.

Medvedev also has benefited from Djokovic essentially sidelining himself because of his refusal to be vaccinated against Covid-19, which led to his deportation from Australia ahead of the Australian Open and is expected to keep him out of the prestigious American tournaments in Indian Wells, Calif., and Miami next month.

Then there is the issue of Medvedev’s nationality. The wider world is not much in the mood to celebrate Russia or Russian athletic achievements at the moment. The country’s invasion of neighboring Ukraine has sparked outrage, protests and international sanctions, and even before the invasion, there were hints of crowds turning against Medvedev.

During his quarterfinal victory over Felix Auger-Aliassime of Canada at the Australian Open, a fan at Rod Laver Arena shouted, “Do it for Ukraine, Felix!”

But Medvedev has spoken out against the war since it began on Feb. 24.

“By being a tennis player I want to promote peace all over the world,” he said in Acapulco. “We play in so many different countries. I’ve been in so many countries as a junior and as a pro.”

He added: “It’s just not easy to hear all this news. I’m all for peace.”

Medvedev’s next tournament is scheduled to be next month’s BNP Paribas Open in Indian Wells, where some players are already planning to show support for Ukraine by wearing outfits that feature blue and yellow, the colors of Ukraine’s national flag.

On Sunday, just hours before he officially became the No. 1-ranked men’s singles player, Medvedev made another plea, this time on social media.

“Today I want to speak on behalf of every kid in the world,” he said. “They all have dreams. Their life is just starting, so many nice experiences to come: first friends, first great emotions. Everything they feel and see is for the first time in their lives. That’s why I want to ask for peace in the world, for peace between countries. Kids are born with inner trust in the world, they believe so much in everything: in people, in love, in safety and justice, in their chances in life. Let’s be together and show them that it’s true, cause every kid shouldn’t stop dreaming.”

Medvedev, like many leading Russian players, moved abroad in his teens to further his tennis career. While his Russian contemporaries Andrey Rublev, 24, and Karen Khachanov, 25, landed in Spain, Medvedev went to southern France and now lives in Monte Carlo, long a sunny and tax-friendly base for tennis stars.

He has been coached by the Frenchman Gilles Cervara since 2016 and speaks fluent French and English — useful skills in a global sport with post-match news conferences and interviews.

But Medvedev, by turns endearing and alienating, is hardly a typical tennis ambassador. He has taunted and criticized crowds when they have turned against him, and he was fined in Australia last month for a tirade against a chair umpire for not policing the coaching that Medvedev believed his opponent, Stefanos Tsitsipas, was receiving illegally during the match from his father, Apostolos.

Tsitsipas was indeed warned for a coaching violation later in the match, but Medvedev, who had called the chair umpire “stupid” and, more cryptically, “a small cat,” was apologetic, as he often is after, in his own words, “losing my mind.”

“I regret it all the time, because I don’t think it’s nice; I know that every referee is trying to do their best,” he said in Melbourne. “Tennis, you know, we don’t fight with the fists, but tennis is a fight. It’s a one-on-one against another player, so I’m actually really respectful to players who never, almost never, show their emotions because it’s tough. Because I get and can get really emotional. I have been working on it.”

Medvedev has a performance psychologist, the Frenchwoman Francisca Dauzet, on his team, and despite his outbursts in Melbourne, his on-court behavior has much improved from his earlier, more combustible years on tour. It has been quite an unexpected journey to the summit, and Medvedev is the 27th man to reach the top spot since the ATP computer rankings began in 1973. He is also the tallest at 6-foot-6: a reflection of the increase in average height among the men’s tennis elite.

Unlike the members of the Big Four, he is not yet a true multi-surface threat: his best results have come on hardcourts. But he clearly has the skills to thrive on grass. Unsurprisingly, the towering Medvedev has a big serve, which he overhauled several years ago, that has been essential to his rise. But what separates him from the tennis giants of the past is his mobility and ability to thrive in extended rallies, often camped far behind the baseline. His groundstrokes, ungainly at first (and second) glance, are unusually flat, staying low off the bounce and often depriving opponents of the chance to attack from their comfort zones.

With his reach, speed and anticipation, he is a world-class defender, but he can also up the tempo by striking the ball early and making surprise moves into the forecourt. Just when an opponent may think he has Medvedev figured out, he changes tactics — and, after winning his first major title at last year’s U.S. Open by stopping Djokovic’s bid for a Grand Slam, Medvedev has now ended Djokovic’s latest run at No. 1 and the Big Four’s even-longer run at the top.

Whatever the timing, that is quite a feat.