[2] The following year, at the age of 17, he was selected by the Moncton Wildcats of the Quebec Major Junior Hockey League in the first round, 39th overall, in the 2013 CHL Import Draft.

[2][3] He soon after made his professional hockey debut with Avangard Omsk during the 2013–14 KHL season, playing two games with the club before being returned to Omskie Yastreby.

The National Hockey League, however, rejected the contract, informing the Oilers that Tkachev was ineligible to be signed by any NHL team until the 2015 off-season because the Collective Bargaining Agreement stated that CHL players needed to play a full season in North America to be eligible if undrafted.

The decision was made on the basis that the Wildcats needed to readjust their roster for the future and to allow Tkachev an opportunity to play in the 2015 Memorial Cup, as the Quebec Remparts were slated to host the event.

[13] Tkachev opted to return to his native Russia to resume his professional career after his KHL right's were traded by Avangard to SKA Saint Petersburg on September 12, 2015.

He made his long awaited NHL debut registering 2 assists in a season opening 6-2 victory over the Vegas Golden Knights on 14 October 2021.

[18] Tkachev made 3 further appearances with the Kings before he was re-assigned to AHL affiliate, the Ontario Reign, for the remainder of the season, collecting 7 goals and 29 points through 41 games.

With limited opportunity with the Kings, in the off-season Tkachev's KHL rights were traded from SKA Saint Petersburg back to original club, Avangard Omsk, in exchange for financial compensation.