Kovalchuk developed in the youth system of Spartak Moscow, joining their senior team in the Vysshaya Liga in 1999. After two seasons with Spartak, he joined the Atlanta Thrashers of the NHL, who selected him first overall in the 2001 NHL Entry Draft. After eight seasons with the Thrashers, he was traded to the New Jersey Devils in 2010, with whom he signed a 15-year, $100 million contract, after a 17-year, $102 million deal was rejected by the NHL. In 2013, he left the NHL to return to Russia, joining SKA Saint Petersburg, where he played for five seasons before returning to the NHL in 2018.