2010-11: Denis Gorbunov played for Crystall Elektrostal's 1994-born team in Russia's Moscow Region. In 15 first group games he scored 5 goals with 4 assists and had 10 penalty minutes.
2011-12: Gorbunov made his pro hockey debut in Belarus as a 17-year-old; skating for Shakhter Soligorsk's second team. In 47 games he scored 21 goals with 29 assists and had 34 penalty minutes.
2012-13: Gorbunov played junior hockey for Belarus-based Dinamo-Shinnick Bobruisk in Russia's MHL. He scored 20 goals with 17 assists and was +2 with 28 penalty minutes in 55 regular season games. Gorbunov scored 1 goal and was -3 with 4 penalty minutes in four playoff games. He skated in three games for Dinamo Minks during the KHL's Nadezhda Cup and was -3 with no points nor penalty minutes. Gorbunov was selected by Baie-Comeau in the first round (51st overall) of the 2013 CHL Import Draft.
2013-14: Gorbunov was part of a balanced scoring attack for Baie-Comeau in his first QMJHL season and played for Russia in the 2013 Subway Super Series. He was a candidate for Russia's squad at the 2013 World Junior Championship but missed the tournament with a knee injury. In 61 regular season games he scored 21 goals with 30 assists and was +29 with 26 penalty minutes as the Drakkar finished first in the East Division. Gorbunov had two assists in two games for Russia during the Subway Series.