[5] In September 2019, he defeated reigning world number 5 and 2-time Roland Garros finalist Dominic Thiem in straight sets in a Davis Cup singles rubber.

[3][14] Ruusuvuori started his year in January at the AGL Loy Yang Traralgon Junior International, reaching the semifinals in both the doubles, with partner Michael Vrbenský of the Czech Republic, and singles.

[15] He then entered the Australian Open, his debut grand slam event, participating in both the boys' singles and doubles.

[16] February saw Ruusuvuori compete in his first Davis Cup match, losing to Nikoloz Basilashvili of Georgia in straight sets.

[18] After not seeing competition in April 2017, Ruusuvuori returned in May, participating in the Italy F13 Futures event, where he lost in the third round of singles qualifying.

Together they reached the quarterfinals, losing to eventual finalists Vasil Kirkov and Danny Thomas of the United States.

Competing at the Nike Junior International in Roehampton, he reached the semifinals in singles and first round in doubles, again partnering Molleker.

[24] He returned to competition in August at Les Internationaux de Tennis Junior Banque Nationale du Canada, losing to Brian Shi of the United States in the second round.

[25] Competing as an unseeded player at the 2017 US Open in September, Ruusuvuori saw his best singles Grand Slam result of the year, reaching the semifinals.

In the semifinals, Ruusuvuori lost to eventual champion Wu Yibing of China in three sets, 6–4, 3–6, 6–7(4), after having two match points.

At the Sweden F4 Futures, he again reached the singles quarterfinals after passing through qualifying, losing to eventual champion Tallon Griekspoor of the Netherlands.

[28] At the ITF Junior Masters, he finished with a 2–1 record in round robin competition, winning matches against Jurij Rodionov of Austria and Marko Miladinović of Serbia while losing to Wu for the second time that year.

[29] Reaching the final, he again faced Wu, this time exacting revenge to come out on top in three sets, 3–6, 6–1, 7–6(4), and claim the title.

As a wildcard entry in Pärnu, he defeated third seed Vladimir Ivanov of Estonia en route to his third quarterfinal showing of the year.

[35] Ruusuvuori again represented his home country in the Davis Cup in February, going 1–1 in singles to help Finland advance over Tunisia 3–2.

5 and 2-time French Open finalist Dominic Thiem in straight sets in a Davis Cup match against Austria for his first top-10 win.

48 in the rankings after the 2022 Queen's Club Championships where he reached the quarterfinals as a qualifier defeating wildcard Jack Draper.

[54] At the 2022 Erste Bank Open in Vienna he defeated Metz champion Lorenzo Sonego, moving closer to the top 40 in the rankings at No.

[58] Representing Finland during the Davis Cup tie against Argentina, Ruusuvuori won both matches that he played beating Pedro Cachin and Facundo Bagnis.

[59] Seeded seventh at the Open Sud de France, he lost his second-round match to eventual finalist Maxime Cressy.

[70][71] He went one step further and defeated 26th seed, Botic van de Zandschulp, in the fourth round, to reach his first Master quarterfinal in his career.

[74] However, due to Frances Tiafoe withdrawing from the tournament after winning the U.S. Men's Clay Court Championships in Houston, Ruusuvuori earned a lucky loser spot into the main draw.

[83] He lost in his semifinal match to sixth seed, home crowd favorite and eventual champion, Tallon Griekspoor.

[84] At the 2023 Western & Southern Open he defeated sixth seed Andrey Rublev, his fourth top-10 win, and reached the third round.

In Stockholm he defeated qualifier Benjamin Hassan but lost to third seed Tallon Griekspoor and fell out of the top 60.

[87][88] He reached his second career final in Hong Kong defeating Benjamin Bonzi, second seed Karen Khachanov, Pavel Kotov and Sebastian Ofner.

[89][90] At the 2024 Australian Open he recorded his 100th win defeating wildcard Patrick Kypson becoming only the second player from Finland to reach this milestone after Jarkko Nieminen.

[91][92][93] At the 2024 ABN AMRO Open in Rotterdam, he reached the quarterfinals defeating seventh seed Ugo Humbert and Jan-Lennard Struff.

At the 2024 Wimbledon Championships he reached the third round of a Major for the first time with wins over Mackenzie McDonald and 11th seed Stefanos Tsitsipas.

He became the third Finnish player to make the third round at the All England Club, joining Pekka Säilä and Jarkko Nieminen.