Bulaga tore an ACL and will miss the season, sources said Monday. The Packers canceled practice Monday and no one from the team was available to comment.
The Milwaukee Journal Sentinel and ProFootballTalk.com earlier had reported the nature of Bulaga's injury.
Just three months ago, coach Mike McCarthy moved Bulaga from right tackle to left tackle; Pro Bowl guard Josh Sitton from right guard to left guard; T.J. Lang from left guard to right guard; and Marshall Newhouse, who started 28 games the past two seasons at left tackle, to right tackle.
McCarthy has said he moved Sitton to left guard to put the team's two best offensive linemen together on the same side to protect quarterback Aaron Rodgers' blind side. Sitton and Bulaga had played next to one another since the 2010 season.
It's unclear when Bulaga was injured Saturday night. He took all of the first-team snaps at left tackle during the scrimmage and was also on the field-goal protection unit at the end of practice.
The Packers would appear to have two options at left tackle: They could move Newhouse, who took over for injured veteran Chad Clifton during the 2011 season, back to left tackle. Or they could insert promising rookie David Bakhtiari, a fourth-round pick, there. Bakhtiari was impressive during the first week of practices in pads, competing at right tackle with Newhouse and Don Barclay.
When Bulaga suffered a season-ending hip injury in November, Barclay started the final six games (including the playoffs) at right tackle, but has been working at center and guard in camp.
The upheaval comes at a time when offensive line coach James Campen was pleased with the way the rejiggered starting five was coming together.
"You know, I think that quite frankly it's exceeded what I thought it would be at," Campen said late last week. "I think they've done a very good job with their footwork. They took advantage of the OTA periods to get adjusted to it. I think they're over that hump. It's just a few little things, new footwork they've got to work on, but I think they've adjusted very well."
The Packers still don't have 2011 first-round pick Derek Sherrod at their disposal. He remains on the active/physically unable to perform list because of the broken leg he suffered in December 2011.
Information from ESPN NFL Insider Adam Schefter and The Associated Press was used in this report.