Callahan, 22, made his NHL debut on March 25 against the Columbus Blue Jackets. He was second on the Grand Rapid Griffins of the American Hockey League with 26 goals and fourth with 44 points in 70 regular-season games.
Callahan was a sixth-round pick (No. 180) in the 2009 NHL Draft.
Nestrasil, 23, had 16 goals and 36 points in 70 games for the Griffins. He was a third-round pick (No. 75) in 2009.
You could see out there that everybody was willing to compete, to sacrifice, even blocking shots to the end. Even in the third when we were up 5-0, guys were still working hard and blocking shots That's a nice feeling also for the future.
— Flames goalie Jonas Hiller after his team's 5-0 win over Carolina