"That's not the reason he's not here," said Jackson, who became the Raiders' offensive coordinator in January 2010 before Russell was released that May. "I think there were several other factors, things that we don't need to get into."
Raiders owner Al Davis, who died Oct. 8, made the final call on Russell, later blaming it on "personal problems."
Jackson said he felt Russell was a "good young man," who improved in their time together. He also said he'd like to see Russell get another chance to return to the NFL.
"I thought he got better, but was he as good as he needed to be?" Jackson said. "Obviously not, because we made the decision to move forward. I wish him nothing but the best."