Taylor suffered an injury which kept him out of action in Week 11 and 12, and Landry was moved to the free safety position in his place. After Taylor was murdered at his home in Miami on November 27, Landry remained in the free safety position across from strong safety Reed Doughty. Landry started all 16 games, recording 95 total tackles (65 solo tackles, 32 assisted tackles), 1.5 sacks and six passes deflected. His impressive rookie season earned him a 2007 Pro Bowl alternate selection and was selected to the 2007 NFL All-Rookie Defensive Team. He also became the first Redskins rookie defensive player to start all 16 games since Champ Bailey in 1999.

Landry made an immediate impact at LSU, starting ten games as a true freshman in 2003 while helping the Tigers win the BCS National Championship. He recorded 80 total tackles, 3.5 tackles for loss, three sacks, two interceptions, four pass-breakups, and one blocked kick. Landry was named to the Freshman All-SEC team, Second Team All-SEC and the First-Team Freshman All-American Team.

In 2005, LSU won the SEC Western Division and the Peach Bowl over Miami. Landry registered 70 total tackles, four tackles for loss, one sack, three interceptions, and eight pass-breakups. Landry was named a First-Team All-SEC and Third-Team All-American by the Associated Press and First-Team All-SEC by the SEC coaches.

After spending the previous two seasons at free safety, Landry was moved back to his natural position of strong safety and started off the season playing at a “Pro Bowl level” according to The Free-Lance Star. In Week 5, he was named the NFC Defensive Player of the Week for his performance against the Green Bay Packers, in which he collected 13 solo tackles, defended a pass, forced a fumble, and intercepted Packers’ quarterback Aaron Rodgers in overtime. His interception would lead to the Redskins’ game-winning field goal. Landry injured his Achilles tendon playing the Eagles in Week 10, and eventually landed on injured reserve December 13, ending his season having only played in 9 games. Landry avoided surgery on his left Achilles tendon and instead received platelet-rich plasma treatments. On December 15, 2011, Coach Mike Shanahan stated that he believed Landry “would’ve been defensive player of the year” for the 2010 season had he not been injured.

Landry was placed on the PUP list during all of preseason. He was taken off the list and placed on the active 53-man roster, but, due to a strained hamstring, missed the first two games of the season. He made his 2011 debut in Week 3 against the Dallas Cowboys, where he made a big hit on Laurent Robinson and later forced a fumble. In Week 12 against the Seattle Seahawks, after receiving a cut block, Landry was forced to leave in the first quarter. Despite coming back for the second half of the game, Landry suffered a groin injury that caused him to miss the next two games. On December 15, he was officially placed on injured reserve after being advised to get surgery on his left Achilles tendon, ending the last season of his rookie contract having played a total of eight games. On January 23, 2012, it was announced that Landry had decided to go with alternative medicine, receiving the stem cell treatment known as AminoMatrix on his left Achilles tendon in hope of avoiding surgery. The Redskins chose not to re-sign Landry, according to reports his departure from the team was mutual.

Landry reached an agreement with the New York Jets on March 19, 2012 on a one-year, $3.5 million contract with $700,000 in guaranteed money. By June 14, 2012, it was reported that Landry’s Achilles tendon was fully healed, but the heel bone connected to the tendon was still healing. With the bone still healing, he was placed on the physically unable to perform list prior to the start of training camp. He was placed on the active roster again on July 26. He made a stellar debut as a Jet during the season opening win against the Buffalo Bills as he led the Jets’ defense in tackles. He made his presence known by making an impressive tackle against Fred Jackson, which took him out for the rest of the game, and forcing a fumble that was recovered by Yeremiah Bell. He had another good performance in Week 3 against the Miami Dolphins after intercepting Ryan Tannehill, he ran the ball back for 18 yards and scored his first career touchdown. Late in the first half of the game, he also landed a hard tackle on Reggie Bush, which made him leave the rest of game. Landry was selected to the 2013 Pro Bowl on December 26, marking the first appearance of his career, having been selected only as a Pro Bowl alternate in 2007 and 2008. By the end of the season, Landry set new career highs of 100 combined tackles and four forced fumbles, as well as recording two interceptions, eight pass deflections, and one touchdown.

Landry signed a four-year, $24 million contract, with $14 million guaranteed, with the Indianapolis Colts on March 13, 2013. He played 12 games in 2013, and had 87 tackles and 2 pass deflections.

On September 29, 2014, Landry was suspended 4 games for violating the NFL policy on performance-enhancing drugs. On February 11, 2015, Landry was released by the Colts. After his release, Landry was suspended for the first 10 games of the 2015 season on March 6, 2015, for another violation of the NFL policy on performance-enhancing drugs.

On November 24, 2015, Landry was suspended for testing positive for PEDs, his third such violation of the league’s performance-enhancing drug policy. This resulted in an indefinite ban as per league rules. He will be eligible to apply for reinstatement 60 days before the 2 year anniversary of his suspension.