He says there might have been a ghost involved.
Kerley spoke to reporters Wednesday. He was officially suspended on Nov. 6. The four-game ban was without pay. Kerley received the discipline for violating the NFL policy on performance-enhancing substances. He was eligible to return to the Jets' active roster on Monday.
"I don't know," Kerley told reporters, according to the New York Post. "There's a lot of ghosts around here. Maybe a ghost put it in me. You know the Ghost of Christmas Past? A ghost might have put it in me. I don't know."
In November, Kerley spoke out against the suspension, vowing to investigate the case.
"While I did not have enough time prior to the deadline to resolve this case, I fully intend to investigate this matter until I am able to figure out what caused the positive test, because I know that I have done nothing wrong," his statement read on social media.
Kerley said he tested positive for the steroid Turinabol.
On Wednesday he said he didn't have time to investigate it.
"It is what it is. I'm back now," Kerley said.
Kerley is not officially back on the Jets' active roster. Jets coach Todd Bowles told reporters that they will make a decision "pretty soon."
The Jets face the New Orleans Saints at 1 p.m. Sunday in New Orleans. New York placed quarterback Josh McCown on injured reserve this week. The Jets have Robby Anderson and Jermaine Kearse listed as their to wide receivers, with ArDarius Stewart, Chad Hansen, JoJo Natson and Kerley listed as backups on their unofficial depth chart.