The team said it would not place Bulger on injured reserve.
Bulger underwent two MRIs on Monday, one on his groin and hamstring and a second for what the team believed was a swollen knee. He also was to be tested for concussion-related symptoms Tuesday after a physically demanding loss to the Arizona Cardinals.
Coach Steve Spagnuolo said the first MRI revealed a strain. Spagnuolo held his news conference Monday before Bulger's second MRI, but had not been optimistic about the quarterback's chance of playing this week.
"Marc Bulger's pretty banged up," the coach said. "Marc's got a few things going on."
Bulger has completed 56.7 percent of his passes for five touchdowns and six interceptions for the Rams (1-9). Backup Kyle Boller will make his third start of the year Sunday against the Seahawks.
Boller has played in three games, completing 57 percent of his passes with two touchdown passes and three interceptions. He finished a 36-17 loss to the Packers after Bulger injured his rotator cuff on a sack and started the next two games, a 35-0 loss to the 49ers and 38-10 loss to the Vikings, but was shaken up in that game and replaced by Bulger.
Spagnuolo was hopeful guard Richie Incognito can return after missing three games plus the bye week with a foot injury.