The home side took an early lead when 25-year-old quarterback faked a handoff to Ben Tate before throwing deep to his wide receiver, who ran in a 62-yard score with just a minute on the clock.
They went further ahead with just over four minutes remaining in the first quarter. This time Keenum launched the ball down the middle and Johnson was at full stretch to gather it in front of him.
Adam Vinatieri had already seen one field goal attempt blocked by JJ Watt when he found up from 30 yards late in the second quarter, but he sent his second attempt between the posts to make it an 11-point game.
However, Keenum picked out Johnson for the third time to extend the Texans' advantage with less than a minute left before half time.