He came up with a muffed punt by San Francisco's Jimmy Williams at the 49ers' 13 to set up the Bears' go-ahead touchdown for a 10-3 lead in the second quarter.
Just because he's a starter, Johnson doesn't expect to be watching from the sidelines on special teams.
"I'd like to still play special teams," he said. "I know (coach) Lovie Smith said that in the beginning he wants the best people out there and if I end up being one of the better guys on special teams I'd still like to play.
"I don't mind playing special teams; in fact that's how I got into the league is playing special teams." Johnson, who is a former linebacker, caught on as an undrafted free agent out of Boise State with the Washington Redskins in 2000 and caught on as a special teams player.
He made 64 tackles the last three seasons on special teams.
"I don't care if I'm blocking the whole time, or running routes, or just playing special teams," Johnson said.
Qasim Mitchell started at left tackle and Smith said he has the starting spot.
However, in the first half Saturday night, Mitchell was inconsistent after having a poor first game against the Rams. He was beaten on a pass rush badly by Andre Carter, forcing Grossman into a wild scramble before eventually throwing the ball away.
In the end, Mitchell really had no competition for the spot. When coaches decided John Tait would start at the right tackle spot instead of left tackle,
"He's made just about every practice and really has been pretty good with what he has done," Smith said of Mitchell.
Starting linebacker Marcus Reese suffered a first-quarter pulled hamstring and left the game.
Reese had been the surprise of training camp in taking a starting spot. Joe Odom replaced him on the field.
Bears wideouts had looked up to Marty Booker, and now they feel like they've lost a leader -- or worse.
"It feels like I lost a brother to another team," wide receiver Bobby Wade said. "Marty was a great leader on this team and obviously a great playmaker. He will be missed, but I guess the way to say it is, it's the nature of the business."