A. J. Klein

Aaron James Klein (born July 30, 1991) is an American football linebacker who is a free agent. He played college football at Iowa State. He was selected by the Carolina Panthers in the fifth round of the 2013 NFL Draft.

Early life
Klein attended Kimberly High School where he was a letterman in football and track. His football team went 37–1 during his career. He led team to back-to-back Division II state championships in his final two seasons. He recorded 121 tackles, five sacks, three forced fumbles and two fumble recoveries as a senior, and his career included 287 tackles, 17 sacks and two interceptions.

In track & field, Klein competed as a sprinter in spring of 2008. During the indoor season, he competed in the 55-meter dash and recorded a personal-best time of 7.01 seconds at the Oshkosh HS Invite. He competed in the 100-meter dash during the outdoor season, earning a 5th-place finish at the WIAA Regional with a time of 11.8 seconds.

Considered a three-star recruit by Rivals.com, he accepted a scholarship offer from Iowa State over offers from Northern Illinois, Western Michigan and Wyoming.

College career
While attending Iowa State University, Klein was a member of the Iowa State Cyclones football team from 2009 to 2012. He played in every game as a true freshman finishing the season with 17 tackles, and also caused and recovered a fumble. He played in 12 games, starting 10, as a sophomore, and finished second on the team in tackles with 111, including eight for loss. He also had three interceptions (returning 2 for touchdowns), four pass deflections, and a fumble recovery. In 2011, he started in all 13 games, recording 116 tackles, including 7.5 tackles for loss and two sacks, seven pass deflections, six pass break ups, and an interception (returned for a touchdown). He was named Big 12 Co-Defensive Player of the Year and earned All-Big 12 first-team honors. In his senior season, he recorded 117 tackles, including 3.5 tackles for loss and one sack, three pass deflections, two pass break ups and an interception (returned for a touchdown). He earned All-Big 12 first-team honors once again.

2013
The Carolina Panthers selected Klein in the fifth round (148th overall) of the 2013 NFL Draft. Klein was the 16th linebacker drafted in 2013. On May 23, 2013, the Carolina Panthers signed Klein to a four-year, $2.35 million contract that includes a signing bonus of $191,300.

Throughout training camp, Klein competed against Chase Blackburn, Jordan Senn, Jason Williams, and Doug Hogue for a role as the primary backup outside linebacker. Head coach Ron Rivera named Klein the backup strongside linebacker, behind Thomas Davis, to begin the regular season.

He made his professional regular season debut during the Carolina Panthers' season-opening 12–7 loss against the Seattle Seahawks. On November 10, 2013, Klein earned his first career start after Chase Blackburn was ruled inactive due to a foot injury he sustained the previous week. Klein collected a season-high five solo tackles and made his first career sack during their 10–9 victory at the San Francisco 49ers in Week 10. Klein sacked 49ers' quarterback Colin Kaepernick for a 14-yard loss during the second quarter. He finished his rookie season in 2013 with 21 combined tackles (18 solo) and two sacks in 16 games and two starts.

2014
During training camp in 2014, Klein competed against Chase Blackburn to be a starting outside linebacker. Head coach Ron Rivera named Klein and Thomas Davis the starting outside linebackers to begin the regular season, alongside middle linebacker Luke Kuechly. In Week 4, he collected a season-high seven combined tackles during a 38–10 loss at the Baltimore Ravens. Klein was inactive for the last two games (Weeks 16–17) due to an ankle injury. He finished the 2014 NFL season with 39 combined tackles (25 solo) in 14 games and eight starts.

The Carolina Panthers finished the 2014 NFL season first in the NFC South with a 7–8–1 record, but Klein was inactive due to his ankle injury as they reached the NFC Divisional Round where they were defeated 31–17 at the Seattle Seahawks.

2015
Klein entered training camp slated as the starting weakside linebacker, but saw competition from rookie first round pick Shaq Thompson. Head coach Ron Rivera named Klein the backup weakside linebacker, behind Shaq Thompson, to begin the regular season. On September 20, 2015, Klein started at middle linebacker after Luke Kuechly was inactive due to a concussion he sustained the previous week. He recorded four combined tackles, one pass deflection, and made his first career interception as the Panthers defeated the Houston Texans 24–17 in Week 2. Klein intercepted a pass by Texans' quarterback Ryan Mallett, that was intended for tight end Garrett Graham, and returned it eight yards during the fourth quarter. In Week 3, he collected a season-high ten combined tackles (six solo) during a 27–22 win against the New Orleans Saints. Klein was inactive for the Panthers' Week 6 victory at the Seattle Seahawks after suffering a concussion during a Week 4 victory at the Tampa Bay Buccaneers. Klein finished the season with 55 combined tackles (39 solo), one pass deflection, one sack, and one interception in 15 games and six starts.

On February 7, 2016, Klein was part of the Panthers team that played in Super Bowl 50. In the game, the Panthers fell to the Denver Broncos by a score of 24–10.

2016
During Week 10 of the 2016 season, All-Pro starting linebacker Luke Kuechly was severely concussed and did not play the rest of the season. Kuechly's injury thrust Klein into a starting role for the Panthers. In his seven starts, Klein made 16 solo tackles, assisted on 13 more and registered one sack.

New Orleans Saints
On March 9, 2017, Klein signed a three-year, $15 million contract with the New Orleans Saints. He suffered a groin injury in Week 14 and was placed on injured reserve on December 19, 2017. He started the first 12 games of 2017, recording 54 tackles, two sacks, and four passes defensed.

Buffalo Bills (first stint)
On March 27, 2020, the Buffalo Bills signed Klein to a three-year, $18 million contract that included $11.30 million guaranteed and a signing bonus of $1.20 million. The signing reunited Klein with Buffalo Bills' head coach Sean McDermott, who previously coached Klein as the Carolina Panthers' defensive coordinator.

Klein was plugged into the starting lineup due to a nagging injury to Matt Milano. Despite struggling throughout much of the first half of the season, Klein had a breakout game against the heavily favored Seattle Seahawks, sacking Russell Wilson twice, including a strip sack which he also recovered that all but sealed a 44–34 win for Buffalo. In Week 10 against the Arizona Cardinals, Klein recorded a team high 10 tackles and sacked Kyler Murray once during the 32–30 loss. In Week 12, following a bye in Week 11, playing at home against the Los Angeles Chargers, Klein recorded another team high in tackles with 14. He also added a sack and three tackles for a loss on rookie Justin Herbert, on the way to a 27–17 Bills victory. Klein was named the AFC Defensive Player of the Week for his performance in Week 12.

Klein was released by the Bills on March 8, 2022, in a cap-clearing move.

New York Giants
On October 3, 2022, the New York Giants signed Klein to their practice squad.

Baltimore Ravens
On October 6, 2022, the Baltimore Ravens signed Klein to their active roster off the Giants practice squad.

Chicago Bears
On October 31, 2022, Klein, a 2023 second round pick, and a 2023 fifth round pick were traded to the Chicago Bears for Roquan Smith. Klein was waived by the Bears on November 16, 2022.

Buffalo Bills (second stint)
On November 17, 2022, Klein was claimed off waivers by the Bills. In the 2022 season, he made his only start, and made nine tackles and broke up a pass, in the Thanksgiving Day game against the Detroit Lions.

Klein re-signed with the Bills on April 17, 2023, for a one-year contract with a base salary of $1.165 million. In July 2023 he told The Buffalo News, “This is the one place I knew I could come to and win the Super Bowl and be around quality people and quality teammates. If this is the end of my journey as far as football goes, I want it to be here in Buffalo.”

He was released on August 29, 2023, and re-signed to the practice squad on September 21. He was promoted to the active roster on October 11. He was released on December 9. Klein was re-signed to the practice squad on January 11, 2024. With Tyrel Dodson injured, Klein was elevated to the team on January 14, 2024, for the January 15 game against the Pittsburgh Steelers. The Bills won 31-17 and he led the team in tackles with 11. Before he was called up, he had bought an RV and was planning a road trip to Key West, Florida, for the weekend. He was not signed to a reserve/future contract after the season and thus became a free agent when his practice squad contract expired.

Personal life
Klein is a Christian. Klein and his wife, Taylor, have a son, Cannon James, whom they adopted in 2019, and a daughter, Bowie Rose, also born in 2019.