A native of Sarasota, Florida, Shields attended Booker High School, where he played football, baseball and ran track.

The contract was for the rookie minimum for undrafted free agents [13][14] Throughout training camp, Shields competed to be the nickelback or dime back against Brandon Underwood and Pat Lee.

[15] Head coach Mike McCarthy named Shields the third cornerback on the depth chart to start the regular season, behind Charles Woodson and Tramon Williams.

[16] On September 12, 2010, Shields earned his first career start and made his professional regular season debut in the Green Bay Packers' season-opener at the Philadelphia Eagles and recorded three combined tackles in their 27–20 victory.

[17] Shields and safety Morgan Burnett became the first rookie defensive back tandem to start for the Packers since the AFL and NFL merged.

[17] On January 23, 2011, Shields started in the NFC Championship game and recorded four solo tackles, deflected two passes, made two interceptions, had a sack, and forced a fumble during a 21–14 win at the Chicago Bears.

He intercepted a pass by quarterback Caleb Hanie, that was intended for wide receiver Johnny Knox, with less than 47 seconds left to seal the Packers' victory and send them to Super Bowl XLV.

[20] On February 6, 2011, Shields collected two solo tackles in the Packers' 31–25 victory against the Pittsburgh Steelers in win Super Bowl XLV.

[22][23] Defensive coordinator Dom Capers retained Shields as the third cornerback on the depth chart, behind Charles Woodson and Tramon Williams, to begin the regular season.

[24] On September 8, 2011, he started in the Green Bay Packers' season-opener against the New Orleans Saints and collected a season-high eight combined tackles (seven solo) and two pass deflections in their 42–34 victory.

[25] On October 16, 2011, he recorded five solo tackles, broke up a pass, and made an interception before exiting the Packers' 24–3 victory over the St. Louis Rams in the third quarter due to a concussion.

The hit by Gibson made direct impact with Shields' helmet and caused a concussion that sidelined him for the Packers' Week 7 victory at the Minnesota Vikings.

Throughout training camp, Shields competed to be a starting cornerback against Davon House, Jarrett Bush, Tramon Williams, and rookie Casey Hayward.

With his absence, head coach Mike McCarthy elected to name Tramon Williams and Jarrett Bush the starting cornerbacks in Week 1.

On September 24, 2012, Shields recorded two combined tackles and a pass deflection in the Green Bay Packers 14–12 loss at the Seattle Seahawks in Week 3.

[30] During the closing seconds of the fourth quarter, Shields was shoved to the ground by Seahawks' wide receiver Golden Tate while he was covering him during a last ditch hail mary by Seattle.

The pass was simultaneously caught by Golden Tate and Packers' safety M. D. Jennings and immediately ruled as a touchdown by one official while his colleague signsled it was an interception.

[31] The play was highly controversial and the NFL would later release an official statement acknowledging the shove by Tate that should've been called for offensive pass interference.

[33] On December 23, 2012, he made one tackle, two pass deflections, an interception, and had his first career sack, dropping Titans' quarterback Jake Locker for an eight-yard loss in the fourth quarter during a 55–7 victory against the Tennessee Titans in Week 16[34] He finished the 2012 season with a total of 28 combined tackles (23 solo), ten passes defensed, three interceptions, and one sack in ten games and eight starts.

[36] Defensive coordinator Dom Capers and cornerbacks coach Joe Whitt Jr. held an open competition between Davon House, Tramon Williams, and Casey Hayward.

[38][39] He started in the Green Bay Packers' season-opener at the San Francisco 49ers and collected a season-high nine combined tackles (seven solo) and two pass deflections in their 34–28 loss.

Head coach Mike McCarthy officially named Shields and Tramon Williams the starting cornerbacks duo to begin the 2014 regular season.

[51][52] On March 8, 2018, the Los Angeles Rams signed Shields to a one–year, $1.00 million contract after he missed the 2017 NFL season while recovering from concussions.

Head coach Sean McVay named him the third cornerback on the depth chart to begin the season, behind starters Aqib Talib and Marcus Peters.