New York Giants Greisen was selected in the fifth round (152nd overall) by the
New York Giants in the
2002 NFL draft. He played mostly on special teams during his first two seasons, and also made his first start in December of his rookie season when
Mike Barrow was injured. He also saw significant playing time at linebacker after injuries to
Barrett Green in 2004 and 2005 opened a starting position. During the 2006 season, he started ten games and recorded an interception. Greisen was released by the team during final preseason roster cuts in 2007.
Baltimore Ravens On September 19, 2007, Greisen signed with the
Baltimore Ravens after the team waived
Dennis Haley. Greisen's defensive playing time sharply declined in the 2008 season, and the Ravens released him on March 13, 2009, in a move that saved the team $716,000 in salary cap space. He spent the season on
injured reserve after sustaining a knee injury in training camp. He was resigned by the team on April 29, 2010. Greisen was waived by the team on August 12, 2010, when the team signed Johnny Williams.
Omaha Nighthawks Greisen was signed by the
Omaha Nighthawks of the
United Football League on September 8, 2010. He spent the 2010 and 2011 seasons with the organization. ==NFL career statistics==