"I was going through a divorce," the 11-year veteran and father of three said. "It's hard playing football when so much is on your mind."
Jammer, 32, allowed six touchdowns in 2011, two more than his season average over the past five seasons. Quarterbacks picked on Jammer to the tune of 10.5 yards per attempts his way last season; he had averaged 7.2 yards per attempts from 2006 to 2010, according to the newspaper.
"Last year, let's just put it out there, was not my best year," said Jammer.
"I would try to shake myself out of it, get the cobwebs out and just think," he added. "But there were so many things to deal with, so much was going through my head. I couldn't focus."
Jammer said he remembered a play last November against the Chicago Bears when he didn't see his man take off downfield, blowing by him.
"I was on the other hash," he said. "For what reason, I don't know. That's when I was like, 'This is bad. I'm mentally shot.'"
Jammer vowed he will be back to his old, pass-deflecting self this season. His teammates and coach Norv Turner deserve it, he said.
"This was the toughest thing I ever had to deal with," Jammer said. "Am I still affected by it? Yes. But will it affect my season this year? No. This will probably be my best year. I owe it to the team. I owe it to Norv, who was one of my biggest supporters. He was there, he stood by me, just knowing what I was going through. I owe him and my teammates a great year."