Sydor originally began his Memorial Cup championship season in the National Hockey League (NHL) with the Kings, but was sent back to the WHL after 18 games.

During his time with Dallas, Sydor became part of the team's "big four" defenceman, which included Derian Hatcher, Sergei Zubov and Richard Matvichuk.

In the regular season leading up to Sydor's first Stanley Cup championship, he matched his career-high 48 points and established a personal best 14 goals.

[2] He played only 49 games with Columbus before being traded to the Tampa Bay Lightning in exchange for prospect Alexander Svitov midway through the season.

Sydor remained with the Lightning for one more season and was then traded back to the Dallas Stars on July 2, 2006, for a 2008 fourth-round draft pick in a salary-dumping move.

Due to a late-season acquisition for defenceman Mattias Norström, Sydor became the odd man out on the Stars' blueline and did not receive an offer from the club.

According to the criminal complaint filed in Anoka County District Court, Sydor's blood alcohol level tested at 0.30, more than three times the legal limit.

[15] Sydor voluntarily entered the NHL/NHL Players' Association Substance Abuse/Behavioral Health Program and admitted himself into an inpatient centre in Malibu, California, on August 22 to seek treatment for alcoholism, earning the respect of fellow Blazers' majority owner Tom Gaglardi.