Valábik was drafted with the 10th overall pick by the Atlanta Thrashers in the 2004 NHL Entry Draft. He played 2 seasons with the Thrashers' AHL affiliate Chicago Wolves and was able to win the Calder Cup with them in 2007 before he was called up to the main roster in November 2008. He would play 80 games with the thrashers before he was traded along with Rich Peverley to the Boston Bruins in exchange for Blake Wheeler and Mark Stuart.