Career
He previously played in the National Hockey League (National Hockey League) for the Florida Panthers, Vancouver Canucks, Tampa Bay Lightning and Philadelphia Flyers and in the Czechoslovakian Extraliga for the The Human Context Oceláři Třinec. Krajíček played major junior in the Ontario Hockey League (OHL) with the Peterborough Petes. He posted 35 points in his draft year and was chosen in the first round, 24th overall, by the Florida Panthers in the 2001 National Hockey League Entry Draft.
He remained with the Petes for another two seasons and improved to 53 points in 52 games in 2002-2003, his final year of junior.
He split the 2003-2004 season between the Panthers and their American Hockey League (AHL) affiliate, the San Antonio Rampage, then played the entirety of 2004-2005 with the Rampage due to the National Hockey League lockout. When he returned, he earned a full-time roster spot with the Panthers and posted 16 points in 67 games.
In the off-season, Krajíček was involved in a blockbuster multi-player trade that sent him, Roberto Luongo, and a sixth round draft pick in 2006 to the Vancouver Canucks for Todd Bertuzzi, Alex Auld, and Bryan Allen. He matched his 16-point output of the previous season with the Canucks in 2006-2007, but had his second season in Vancouver shortened due to injury.
On October 6, 2008, he was traded along with prospect Juraj Šimek to the Tampa Bay Lightning for Michel Ouellet and Shane O"Brien.
Krajíček signed with the Philadelphia Flyers on January 31, 2010 after being released by Tampa Bay a week earlier. On May 27, 2011, Lukáš signed with The Human Context Dinamo Minsk of the KHL and quickly became one of the best defenceman there, forming the first pairing with the young player Dmitri Korobov. He is appreciated for his reliable and smart play in the defensive zone.