FOXBOROUGH, Mass. -- New England Patriots cornerback J.C. Jackson is dealing with "mental health issues," his agent Neil Schwartz told ESPN's Adam Schefter on Sunday after Jackson was active for the team's 27-17 loss to the Kansas City Chiefs but did not play and wasn't spotted on the sidelines.
Jackson's status was the first topic coach Bill Belichick was asked about after the game.
Belichick simply said Jackson wasn't available. When asked why Jackson was on the game-day roster if he wasn't available, Belichick responded: "He wasn't available. Just leave it at that."
One Patriots player expressed concern for Jackson in the locker room after the game but was unsure of the circumstances that led to Jackson not playing. Jackson's absence led to rookie Alex Austin starting in his place.
"I found out right when the game started that my number was called," Austin said. "It was a surprise."
Teams are required to declare their inactive players 90 minutes before kickoff, and at that point, the Patriots were planning on Jackson being ready for kickoff at 1 p.m. ET. As a result, they declared third-year cornerback Shaun Wade inactive.
But with Jackson suddenly unavailable and Wade inactive, the Patriots were short-handed at cornerback against Chiefs quarterback Patrick Mahomes, who finished 27-of-37 for 305 yards, with two touchdowns and two interceptions.
Veteran Jonathan Jones, Austin and slot Myles Bryant were the only cornerbacks left on the game-day roster, and Jones departed with a knee injury at one point before returning.
Belichick compared Jackson's absence to a situation in which a backup is thrust into action because of injury.
"We all know that when a game starts, anything can happen. [This] happened a little bit before that," he said. "[Austin] was ready to play, expected to play [and] played a lot. It's everybody's job to be ready to go."
Jackson, 28, was acquired from the Los Angeles Chargers in a trade on Oct. 5. He had fallen out of favor in Los Angeles after signing a five-year, $82.5 million deal in March of 2022 and said returning to New England -- where he began his career from 2018 to 2021 -- felt like coming home.
After quickly elevating to a starting role as the Patriots had lost rookie Christian Gonzalez to a season-ending shoulder injury, Jackson didn't make the team's trip to Germany for a Nov. 12 game against the Colts. He confirmed to MassLive.com that he missed "bed checks" at the team hotel the week before, which led to the discipline of not traveling to the game.
"I would say mentally I'm getting better. The past year and a half, two years has been up and down for me mentally," Jackson told MassLive.com upon his return to the team. "You see us in those little, small helmets but as we walk out these doors, we're dealing with reality and what a normal person has to deal with."
Entering Sunday, Jackson had started six games for the Patriots this season, totaling 25 tackles and six passes defended.