More details have emerged about New England Patriots cornerback J.C. Jackson and his absence Sunday.

Jackson did not play on Sunday in New England's 27-17 loss to the Kansas City Chiefs. The cornerback was expected to play and was active for the game. But Jackson's agent Neil Schwartz confirmed his client is “dealing with mental health issues,” per ESPN's Adam Schefter.

Patriots coach Bill Belichick refused to elaborate on Jackson's absence, saying only that “he wasn’t available.” Despite being active, Jackson did not participate in warmups with the team and was not on New England's sideline during the game.

The issue that Jackson is dealing with did not arise until after the team had to designate players active or inactive for the game day roster. His teammates did not know about Jackson not being available until just before the start of the game.

Rough day for Patriots secondary

Jackson's not being able to play resulted in few options for the Patriots in the secondary. Cornerback Shaun Wade was a healthy scratch on Sunday, leaving Belichick with just Alex Austin, Jonathan Jones, and Myles Bryant at the cornerback position.

Bryant was surprised by the development, admitting the situation “was something I didn’t quite expect going into the game,” per MassLive. “Nevertheless, just going out there playing and just trying to help the team any way I can.”

Facing a depleted secondary ended up helping to get Patrick Mahomes back on track. The Kansas City quarterback threw for 300 yards for the first time since October 22 in the win. He was picked off twice however.