In January–February 2014, making his senior international debut, he finished ninth at the Bavarian Open and fifth at the Dragon Trophy before taking the silver medal at the Hellmut Seibt Memorial.

He competed at the 2014 World Junior Championships in Sofia, Bulgaria, but was eliminated after placing thirtieth in the short program.

His final event of the season was the 2015 World Junior Championships, held in March 2015 in Tallinn, Estonia.

He reached the free skate at two ISU Championships – the 2016 Europeans in Bratislava, and the 2016 Junior Worlds in Debrecen, Hungary.

He placed second in the short program at the JGP Poland in Gdańsk, but his placement in the free skate (tenth) dropped him to sixth overall.

Returning to the senior level, Rizzo won gold at the 2017 CS Warsaw Cup, having placed first in both segments ahead of Switzerland's Stéphane Walker and Canada's Liam Firus.

In December, he won the national title and was selected to represent Italy at the 2018 Winter Olympics in South Korea.

He placed tenth in the short program and third in the free skate, winning the bronze medal overall with a personal best score of 247.08 points and achieving his first podium finish at a senior-level ISU Championship.

Introducing the quad toe loop into the short program, he finished second there and then placed first in the free skate to win the gold medal.

[9] At the World Championships in Japan, Rizzo placed fifth in the short program with a new personal best score, tenth in the free, and seventh overall.

[10] In the summer, Rizzo trained at the Toronto Cricket, Skating & Curling Club under Brian Orser, working to acquire more quadruple jumps for the coming season.

In the short program, he placed eighth after underrotating his quadruple toe loop and falling on his combination jump.

[12] At the 2019 Cup of China, Rizzo placed third in the short program despite falling on his triple Lutz and consequently missing his combination.

[17] With pandemic-related travel restrictions in place, Rizzo made his season debut at the 2020 CS Nebelhorn Trophy, an event attended by only skaters training in Europe.

[26] Rizzo returned to his former coach Franca Bianconi, and also added retired pairs skater Ondřej Hotárek to his team.

[27] He made his season debut at the 2021 CS Finlandia Trophy, where he overcame a poor short program to win the free skate and place sixth overall.

[37] After winning his second national title, Rizzo competed at the 2023 European Championships, finishing second in the short program, despite underrotating his attempted quad loop.

[28] Appearing on the Grand Prix at the 2023 Skate Canada International, he finished seventh in the short program after underrotating both of his attempted quad jumps.

In the free skate he performed cleanly but for a triple Axel stepout, finishing second in the segment and rising to third place overall.

[46] He went on to place fourth at the 2023 Grand Prix of Espoo, and expressed frustration at his free skate choreographic sequence being deemed invalid.

A second-place free skate with only one mistake, a fall on a triple Axel, lifted him to third overall, and he claimed his third European medal.

[52] Rizzo competed at his first competition post-surgery at the 2024 Budapest Trophy in early October, where he won the gold medal.