"I can't really go into the details of the situation, but I can let people know that I'm obviously disappointed in decisions that I made that got me in this situation," the third-year pro said after practice.
"I'm definitely disappointed in myself. I let my team down ... a lot of people down. The fans, I'd like to apologize to them. ... I'll be out four games and I'm apologetic. When I come back, I'm hoping to get back on track and move on."
Although the 24-year-old defensive back declined to give a specific reason for the discipline, he did say the suspension "was not a shock because I knew the situation I was in."
"It was something that was before I got into this league, but it kind of lingered on. ... I definitely have some off-the-field issues I have to address for the well-being of myself and the well-being of this team," Jackson said.
A fourth-round draft pick out of Syracuse in 2007, Jackson has started every game over the past two seasons.
Citing confidentiality rules, general manager Mark Dominik declined to discuss specifics about the suspension.
"It's disappointing news. ... He's a good young player. It's a blow to the team," Dominik said.
Jackson, who has three career interceptions, can practice and play in Tampa Bay's three remaining preseason games. Sixth-year pro Will Allen will take over the starting free safety job.
"I felt like Will played well in our [first preseason] game, but it's disappointing," Dominik said. "It's something we're going to deal with. It's something Tanard is dealing with ... and we have to move forward."