The NFL Network reported earlier Saturday that Bulaga had surgery to repair a torn meniscus.
The meniscus tear was apparently discovered in subsequent tests following the injury. A source said Thursday night that Bulaga had a sprained MCL, which does not require surgery, but did not suffer a season-ending ACL tear. However, additional tests were needed to determine whether he sustained any other damage, the source said.
It's the same knee Bulaga blew out in August 2013, when he tore his ACL in a preseason scrimmage. He missed that entire season after undergoing reconstructive surgery and has played with a brace on that knee ever since. He was wearing it Thursday in practice.
Last season, Bulaga credited that brace with saving him from another serious knee injury when he went down in the season opener at Seattle. Rather than a complete knee blowout, he suffered only a sprained MCL and returned after missing just one game.
This past offseason, the Packers gave Bulaga a five-year, $33.75 million contract shortly before he was scheduled to become a free agent.
Packers coach Mike McCarthy offered no injury details on Bulaga other than to rule him out on Friday for Sunday's game against the Seahawks. He also declined to name a replacement starter at right tackle, but the most likely choice is Don Barclay, despite his preseason struggles. Barclay missed all of last season because of a torn ACL, but he started 14 games in 2013 when Bulaga missed the season with a torn ACL.