Johnson will miss Sunday's game against the Detroit Lions as punishment for being at a bar last week, when his friend was shot to death. The incident happened less than 48 hours after he was arrested on misdemeanor weapons charges.
Bears general manager Jerry Angelo said the team had two options: to release Johnson or suspend him. The decision was made, Angelo said, after discussions with the NFL, Bears management, coach Lovie Smith and players.
"Collectively, as an organization -- ownership, coaches, players, myself -- we all agreed that the right thing to do was to keep Tank and keep working with him," Angelo said of a decision that will certainly draw criticism.
"We know we're vulnerable going forward. I'm not going to sit here and tell you I'm 100 percent on board and trust all the things that we've talked to Tank about," he said.
Johnson was arrested Thursday and the following night was at a night club when his friend, Willie B. Posey, was shot and killed. Johnson is not a suspect in the death.
Posey had also been arrested Thursday on drug possession charges when Gurnee police raided Johnson's home.
On the day after his arrest, Johnson publicly apologized and Angelo said it was time for the third-year player to start being accountable for his actions.
"The one-game suspension falls under conduct detrimental to the team based on his decision to go out on Friday night, creating a personal tragedy, a major distraction," Angelo said. "He crossed the line and we acted on that."
Johnson, who will seek counseling -- his idea, according to Angelo -- said he knows he must change or his career with the Bears will be over.
"I don't believe the team has to tell me it's my last chance, I know the opportunity that I have in front of me and it's great, it's immense and to squander that opportunity would be a tragedy at this point and that's not gonna happen," Johnson said.
Posey had been living at Johnson's home at the time of the raid. The day after their arrests, they went to Ice Bar in Chicago's River North area where Posey was shot during a fight early Saturday morning.
"It was a bad decision on my part. For whatever reason, I was out of my house, it was a bad decision, and for that decision I lost my best friend in the world," Johnson said. "So that's a decision that I will live with for the rest of my life."
How Johnson's latest arrest will affect an earlier probation is not clear. He is scheduled for a court date Jan. 9.
Johnson was sentenced to 18 months' probation and 40 hours community service in November 2005, after pleading guilty to a misdemeanor charge stemming from an arrest in which a nightclub valet reported seeing him with a handgun in his sport utility vehicle.
Johnson was also arrested last February after a confrontation outside a Chicago nightclub, but those charges were dropped after the police officer he allegedly fought with decided not to pursue the case.
Johnson was inactive Sunday when the Bears beat Tampa Bay 34-31 in overtime to clinch home-field advantage in the NFC playoffs. Johnson has been a starter at defensive tackle along with Tommie Harris, who will miss the rest of the season after surgery on a torn hamstring muscle.
Angelo said he didn't know what punishment the league might dole out.
"We can't answer that. That'll come under the personal conduct policy," he said. "There are some misdemeanor charges. That's going to be reviewed and done through the league and we'll just see how that unfolds."