How valuable is healthy 'Hawks O-line?

The Seattle Seahawks are 4-0 on the season and are regarded as the prohibitive favorite to come out of the NFC this year. This week the Seahawks take on the Indianapolis Colts on the road. Depending on the sportsbook, the Seahawks are anywhere from 1-point to 3-point favorites. How much is that number and movement dictated by the injuries to the offensive line?