Sedlak, a native of the Czech Republic, was selected by the Columbus Blue Jackets in the sixth round (No. 158) of the 2011 NHL Draft. He came to North America and spent two seasons with Chicoutimi of the Quebec Major Junior Hockey League and three seasons in the American Hockey League.

In 2015-16, he helped Lake Erie win the Calder Cup with 16 points (nine goals, seven assists) in 17 games.

Sedlak became a shutdown forward with the Blue Jackets, but had 13 points (seven goals, six assists) in 62 games during his rookie season. He scored his first NHL goal in a 4-1 win against the Detroit Red Wings on Dec. 9, 2016, doing so against his Czech Republic countryman Petr Mrazek.