It's impossible to know initially how severe a concussion will turn out to be. Some concussions knock out players for weeks, while other times a player is back in the lineup without missing a full game.
Johnson, who leads the NFL in receptions through two weeks, was injured in the fourth quarter against the Tennessee Titans.
Johnson's expected return sets up a fascinating matchup this weekend in Baltimore. The Ravens' defense bounced back with a strong Week 2 effort, and they have a strong group of cornerbacks on paper. But that paper was shredded in Denver during the season opener, and the Ravens will be starting rookie safety Matt Elam for the first time against Houston's great wideout combination of Johnson and rookie DeAndre Hopkins.