In exchange for Steckel, Toronto acquired winger Ryan Lasch and Anaheim's seventh-round pick in the 2014 NHL Entry Draft. Lasch won the Finnish Elite League scoring title last season with 24 goals and 62 points.
Lasch, a 26-year-old native of Lake Forest, Calif., also suited up for the U.S. at the 2012 IIHF world championship and had two assists in seven games in the tournament.
The former St. Cloud State forward amassed 79 goals and 104 assists in 161 career collegiate games from 2006-10 and played 19 games for the Ducks' AHL affiliate in Norfolk this season, and is expected to join the Toronto Marlies.
Steckel, 31, was acquired by the Leafs in a trade with the New Jersey Devils in 2011 and had one assist in 13 games this season. The Milwaukee, Wis. native has 32 goals and 41 assists in 398 career games with the Washington Capitals, Devils and Leafs.
Anaheim general manager Bob Murray said the six-foot-six centre is a welcome addition, and comes with a seal of approval from current Ducks head coach Bruce Boudreau.
"Adding David Steckel gives us another big body and depth up the middle," Murray said. "He comes highly recommended from Bruce [Boudreau]. Faceoffs have been something of a concern for us the last few seasons. Steckel is a tremendous faceoff man and penalty killer, something that will really help our club."
He played for the Capitals and the AHL's Manchester Monarchs under Boudreau.
After acquiring Steckel, the Ducks reassigned left wing Patrick Maroon to Norfolk. He has two goals in 11 games for Anaheim this season.
Anaheim also reassigned goalie Jeff Deslauriers to Fort Wayne of the ECHL on Friday, indicating Viktor Fasth is ready to return from an upper-body injury that sidelined him for the past two games.
Lupul has said he expects to return from a fractured forearm when Toronto hosts the Winnipeg Jets on Saturday on Hockey Night in Canada (CBC, CBCSports.ca, 7 p.m. ET).