He was selected by the San Diego Chargers in the second round of the 2011 NFL draft and also had stints with the New York Jets, Houston Texans, Oakland Raiders, Detroit Lions, Jacksonville Jaguars, and Baltimore Ravens.

According to the Tigers' coaches though, it was his football IQ that made him stand out, along with an impressive showing at the NFL combine where he posted a 38-inch vertical leap and put up 26 bench-press repetitions at 225 pounds, second-most among all defensive backs.

[7][8] Head coach Norv Turner named Gilchrist the third cornerback on the depth chart to begin the regular season, behind Quentin Jammer and Antoine Cason.

[9] He made his professional regular season debut in the San Diego Chargers' season-opener against the Minnesota Vikings and recorded one tackle in their 24–17 victory.

His interception came off a pass attempt by quarterback Chad Henne that was originally intended for tight end Anthony Fasano in the first quarter.

[19] In Week 13, Gilchrist started at strong safety after Atari Bigby and Darrell Stuckey were inactive due to injuries.

[24] On May 5, 2013, it was reported that Gilchrist would attempt to move to strong safety during training camp after the Chargers released Atari Bigby.

[19] He competed for the job at strong safety against Darrell Stuckey, Brandon Taylor, Sean Cattouse, and Jahleel Addae.

[27] He started all 16 games and recorded a total of 77 combined tackles (59 solo), five pass deflections, two interceptions, a forced fumble, and a sack.

[28] Gilchrist entered training camp slated as the starting strong safety, but competed against Jahleel Addae to retain the role.

He intercepted a pass attempt by Shaun Hill, that was intended for wide receiver Kenny Britt, and sealed the Chargers' victory at the end of the fourth quarter.

[32] He completed the season with 76 combined tackles (59 solo), five passes defensed, two forced fumbles, an interception, and a sack in 16 games and 16 starts.

[38] On September 21, 2015, Gilchrist made four combined tackles, a pass deflection, and recorded his first interception as a member of the New York Jets during a 20–7 win at the Indianapolis Colts in Week 2.

Head coach Todd Bowles named Gilchrist the starting free safety to begin the 2016 regular season.

[43][5][4] Throughout training camp, he competed to be the starting strong safety against Corey Moore, Lonnie Ballentine, and Kurtis Drummond.

[44] Head coach Bill O'Brien named Gilchrist the backup free safety, behind Andre Hal, to begin the regular season.

[47] He finished the season with 56 combined tackles (45 solo), six pass deflections, an interception, a forced fumble, and a sack in 16 games and 13 starts.

[58] Gilchrist had toughness and discipline instilled at home at an early age from his father, Ronny, a retired United States Marine.