He played college football at Georgia Tech and was selected by the Green Bay Packers in the third round of the 2010 NFL draft.

Burnett was named to a number of All-ACC and All-American teams, including Pro Football Weekly's 2008 All-America first-team.

[11] Burnett entered training camp competing for the job as the starting strong safety against veterans Atari Bigby and Charlie Peprah.

[16] In Week 4, Burnett made three solo tackles before leaving the 28–26 win against the Detroit Lions in the second quarter after suffering an injury.

[17][18] Burnett finished his rookie season with 14 combined tackles (12 solo), one pass deflection, and an interception in four games and four starts.

The Packers finished the 2010 season second in the NFC North with a 10–6 record and went on to win Super Bowl XLV after defeating the Pittsburgh Steelers 31–25.

[19] Burnett returned as the de facto starting strong safety in 2011 after Atari Bigby departed in free agency.

He started the Green Bay Packers' season-opener against the New Orleans Saints and collected a career-high 14 combined tackles (seven solo) during a 42–34 victory.

The following week, he collected eight solo tackles, two pass deflections, an interception, and made his first career sack on quarterback Cam Newton in the Packers' 30–23 victory at the Carolina Panthers.

[22] He finished the 2011 season with 107 combined tackles (78 solo), a career-high 11 pass deflections, three interceptions, and a sack in 16 games and 16 starts.

[24] On September 30, 2012, Burnett recorded a season-high 14 combined tackles (eight solo) and deflected a pass during a 28–27 victory against the New Orleans Saints.

[11][28] Head coach Mike McCarthy named Burnett the starting free safety, alongside M. D. Jennings, who replaced Charles Woodson after his departure to the Oakland Raiders.

[29] On August 23, 2013, Burnett made one tackle before leaving the Packers' third preseason game against the Seattle Seahawks with a hamstring injury.

[23] The Packers finished first in their division with an 8-7-1 record, but were eliminated after losing in the NFC Wild Card game for the second consecutive season.

[31] During the off-season, the Green Bay Packers opted to not resign M. D. Jennings and moved Burnett back to strong safety in his place.

[34] He returned in Week 11 and recorded six combined tackles, a pass deflection, and sacked Jay Cutler during the Packers' 55–14 win against the Chicago Bears.

[35] He finished the 2014 season with a career-high 130 combined tackles (94 solo), four pass deflections, 1.5 sacks, and an interception in 15 games and 15 starts.

On January 18, 2015, Burnett collected ten combined tackles (eight solo), a pass deflection, an interception, and sacked Russell Wilson in a 28–22 loss at the Seattle Seahawks.

[36] On August 29, 2015, Burnett recorded four solo tackles before leaving the Packers' 39–26 loss to the Philadelphia Eagles in the third preseason game due to a calf injury.

The following week, he collected a season-high ten combined tackles (eight solo) and broke up a pass as the Packers were routed 38–8 at the Arizona Cardinals.

[43] On November 6, 2017, he made five combined tackles during a 30–17 loss to the Detroit Lions before leaving in the fourth quarter after sustaining a groin injury.

[48] In week 11 against the Pittsburgh Steelers, Burnett intercepted a pass thrown by former teammate Mason Rudolph before tearing his Achilles in the 21–7 win.