He played his first game with the Leafs on 5 October 2005 during the season opener against the rival Ottawa Senators, and registered a minor penalty.

[9] On 4 April 2014, he was nominated by the St. Louis chapter of the Professional Hockey Writers' Association for the Bill Masterton Memorial Trophy.

[12] Steen finished his career fourth in games played, sixth in assists, and fifth in points in Blues franchise history.

[13] Steen spent the 2023-24 season working in the St. Louis Blues hockey operations department as a European development consultant.

As Steen was born in Winnipeg during his father's tenure with the Jets, he has dual Canadian and Swedish citizenship; he has chosen to represent Sweden in international hockey competition.

His death was the motivation for Alex, along with family members, to create the Amadeus Steen Foundation to raise funds for, and offer support for, infant and child health care.