A native of Chelyabinsk, Russia, the 27-year-old defenseman spent the past three seasons playing for CSKA Moscow in the Kontinental Hockey League. He scored 23 points (seven goals, 16 assists) in 53 games last season.
Nesterov last played in the NHL in 2016-17, when he scored 17 points (four goals, 13 assists) in 48 games for the Tampa Bay Lightning and Montreal Canadiens.
"Our guys felt that he's really taken a big step forward," Flames general manager Brad Treliving told The Athletic. "A little older, a little more experience, all those types of things. Obviously, you've got to get him here and see how it all plays out, but we certainly think there's some upside with him.
"You've seen it before with certain guys who return to the NHL] a little wiser, with a little more experience. Hopefully, you're better prepared for it. We think he's a good player. We thought this made sense for us."
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Selected by the Lightning in the fifth round (No. 148) of the 2011 NHL Draft, Nesterov has scored 33 points (nine goals, 24 assists) in 132 regular-season games with Tampa Bay and Montreal, and seven points (one goal, six assists) in 28 Stanley Cup Playoff games.
"Over there (in the KHL), he plays in all situations," Treliving said. "Kills penalties, plays on the power play. He's got a big shot. Where that translates here, we'll see. It's a different game over there, so you have to be careful, but he's entering the prime of his career."
