While making his way up the ranks as an offensive defenseman, Klein evolved into a shot-blocking, shutdown style player.
The native of Kitchener, Ontario, was drafted by the Nashville Predators in the second round (No. 37) of the 2003 NHL Draft. During his draft year with Toronto of the Ontario Hockey League, Klein had 11 goals and 44 points in 67 games and added one goal and 10 points in 17 playoff games. In 2003-04 he scored six goals and 29 points in 46 games, then had 10 goals and 21 points in 22 playoff games as Guelph won the OHL championship.