He played quarterback and free safety and returned punts and kickoffs, helping prep team win two consecutive state titles as a junior and senior.

Greenway was named the Big Ten Conference's joint Defensive Player of the Week vs. Arizona State, and won the Hustle Team Award at Iowa.

[10] On August 14, 2006, Greenway tore his ACL in his left leg while covering a kickoff in the first quarter of the Vikings' 16–13 loss to the Oakland Raiders in their first preseason game.

[12] The Minnesota Vikings hired Leslie Frazier as their new defensive coordinator after Mike Tomlin accepted the head coaching position with the Pittsburgh Steelers.

[14] He made his professional regular season debut and first career start in the Minnesota Vikings' season-opener against the Atlanta Falcons and recorded ten combined tackles (four solo) in their 24–3 victory.

[15] In Week 12, Greenway made three solo tackles, a pass deflection, and returned an interception for his first career touchdown in the Vikings' 41–17 win at the New York Giants.

Greenway started all 16 games in 2007 and recorded 105 combined tackles (78 solo), four pass deflections, two forced fumbles, two interceptions, and one touchdown.

[18] On September 21, 2008, Greenway recorded nine combined tackles and made his first career sack on quarterback Jake Delhomme during a 20–10 win against the Carolina Panthers in Week 3.

In Week 11, he collected a season-high 16 solo tackles, made a pass deflection, and a sack in the Vikings' 13–10 loss at the Tampa Bay Buccaneers.

On January 4, 2009, Greenway recorded ten combined tackles (nine solo) during the Vikings' 26–14 loss against the Philadelphia Eagles in the NFC Wildcard Game.

[19] On September 20, 2009, Greenway recorded four combined tackles, deflected two passes, and made a career-high two interceptions during a 27–13 victory at the Detroit Lions in Week 2.

[21] In Week 8, he collected a season-high 11 combined tackles (ten solo) and broke up one pass in the Vikings' 38–26 win at the Green Bay Packers.

On January 17, 2010, he recorded six combined tackles, a pass deflection, and a sack in a 34–3 win against the Dallas Cowboys in the NFC Divisional Round.

[25] On October 24, 2010, he tied his season-high of 12 combined tackles (ten solo) in the Vikings' 28–24 loss at the Green Bay Packers in Week 7.

[25] On November 22, 2010, the Minnesota Vikings fired head coach Brad Childress after they lost 31–3 to the Green Bay Packers and fell to a 3–7 record.

On December 24, 2011, Greenway tied his season-high of 16 combined tackles (four solo) and broke up a pass during a 33–26 victory at the Washington Redskins in Week 16.

[33] On January 9, 2012, it was announced that Greenway would play in the 2012 Pro Bowl as a replacement for Lance Briggs who was unable to participate due to an injury.

[36] He started in the Minnesota Vikings' season-opener against the Jacksonville Jaguars and recorded 13 combined tackles (nine solo) and a season-high two pass deflections in their 26–23 victory.

[37] On October 5, 2012, Greenway was fined $21,000 for unnecessary roughness after he struck wide receiver Calvin Johnson in the head and neck area.

[42] On January 5, 2013, Greenway recorded 11 combined tackles (ten solo) as the Vikings lost 24–10 at the Green Bay Packers in the NFC Wild Card Round.

Greenway intercepted a pass by Steelers' quarterback Ben Roethlisberger, that was originally intended for wide receiver Emmanuel Sanders, in the third quarter.