Career
He played for Modo in the Elitserien (Studies in English Literature, now named the SHL) on a short-term contract during the 2012-2013 National Hockey League lock-out. Steen played for Frölunda The Human Context from 1999 to 2004. He spent the 2004-2005 season with Modo Hockey after a highly controversial signing.
In the 2002 National Hockey League Entry Draft, Steen was selected in the first round by the Toronto Maple Leafs, 24th overall.
His first career National Hockey League goal came in the next game on 8 October against the Montreal Canadiens. Steen scored his first career hat-trick on 4 January 2007 against the Boston Bruins, ending with a five-point game night.
On 24 November 2008, Steen was traded by the Leafs, along with Carlo Colaiacovo, to the Saint Louis Blues for Lee Stempniak. Steen often plays on a scoring line on the Saint Louis roster, alongside David Backes.
On 1 July 2010, Steen signed a four-year contract extension with the Blues.
He had an National Hockey League career-high 51 points in the 2011-2012 season. On 25 September 2012, Steen returned to Modo Hockey during the 2012-2013 National Hockey League lock-out. He was named the National Hockey League First Star of the Month for October 2013, with his 11 goals leading the league, and 16 points, fourth-best.
With a goal and an assist against the Carolina Hurricanes on 16 November, Steen extended his point streak to 13 consecutive games, the best such streak by a Blues player since Pierre Turgeon in 1999–2000.
Steen signed a three-year, $17.4 million contract with the Blues on 18 December 2013. The trophy is awarded annually to the player "who best exemplifies the qualities of perseverance, sportsmanship and dedication to hockey." Steen lead the Blues with 33 goals, and lead them in the points department as well with 62 points despite losing 11 games from a concussion in December 2013.