2008-09: Yaroslav Kosov trained in the Magnitogorsk sports school as well as competing with the Metallurg '93 team.
2009-10: Kosov played for Metallurg Magnitogorsk-93. He was selected by Metallurg in the 3rd round (70th overall) of the KHL draft.
2010-11: Kosov scored 11 goals with 10 assists in 43 games for Stalnie Lisi (Metallurg Magnitogorsk' junior team) during the MHL regular season. In 17 playoff games, he scored six goals with 1 assist as Stalnie Lisi (Steel Foxes) advanced to the Kharlamov Cup finals and finished second to Red Army. Kosov was not listed on Central Scouting's final European skaters rankings but was selected by the Florida Panthers in the 5th round (124th overall) in the 2011 NHL Draft.
2011-12: Kosov appeared in 27 KHL games with Metallurg Magnitogorsk and also played with the club's MHL junior team the Steel Foxes. He also skated in the 2012 U20 World Junior Championship for Russia. Kosov scored 4 goals with 5 assists and was plus-six with 6 penalty minutes; averaging just over 8 minutes of ice time per game with Metallurg. Magnitogrsk finished second in the Kharlamov Division and reached the East Conference finals. Kosov was minus-two in seven playoff games; averaging less than three minutes of ice time. In 12 games for Steel Foxes he scored 6 goals with 4 assists and was plus-five with 6 penalty minutes. Kosov scored 2 goals with 2 assists and was plus-five in seven games at the WJC. Russia defeated Finland in the bronze medal game.
2012-13: Kosov appeared in 40 KHL games with Metallurg Magnitogorsk as a 19-year-old and played for Russia in the 2013 World Junior Championship in Ufa. Averaging just under nine minutes of ice time with Metallurg, he scored 4 goals with 3 assists and was -6 with 10 penalty minutes. Magnitogorsk finished third in the Kharlamov Division and lost to Salavat Yulaev in a seven-game first round series. Kosov saw limited ice time in five playoff games and was -1 with no points nor penalty minutes. In seven games at the WJC he scored 3 goals with 1 assist and was +3 with 2 penalty minutes. Russia defeated Canada in overtime in the bronze medal game.
Kosov has the ideal size for a power forward and possesses above average stick-handling and passing skills. He is strong and quick on his skates and drives the net with authority. Although he does not have a sniper’s mentality, he controls the puck well in traffic, and has the kind of hand-eye coordination that allows him to get the puck out of a pile of skates and put it in the back of the net.
Kosov will play another year for Metallurg Magnitogorsk in the KHL, and should see increased ice time now that he has a couple of seasons behind him. He needs to begin getting regular shifts in the offensive zone in order to continue to progress into the type of power winger that the Panthers hope he can become. If he cannot get offensive ice time, he might be better off coming over to North America for a season of AHL play in order to continue his development.