Toropchenko was an alternate captain for the HK MVD Balashikha in the Junior Hockey League (MHL) before being drafted fourth overall by the Guelph Storm for the Ontario Hockey League (OHL) in the 2017 CHL Import Draft.

In his sophomore season, he played 62 games with 17 goals and 26 assists, helping the Storm win their fourth J. Ross Robertson Cup in the 2019 OHL playoffs.

[5][6] On 13 April 2018, Toropchenko made his professional debut with the Blues' then AHL affiliate, the San Antonio Rampage, in a 4–2 loss against the Texas Stars.

[13] On 14 December 2021, after the Blues suffered a COVID-19 outbreak, Toropchenko made his NHL debut in a 4–1 win against the Dallas Stars.

[2][15] His father, Leonid, was the 260th overall pick for the Pittsburgh Penguins in the 1993 NHL Entry Draft and played 14 seasons of professional hockey in Russia and North America.