I don't think we'll ever know the truth (and it doesn't really matter).but he was about 10 yards away from the returner when the fair catch was signaled, with no blockers in between. Clear line of sight. If he wasn't looking at the returner making the fair catch call, I don't know where he possibly could have been looking.
His momentum from his initial running pace was taking him to the left of the returner. Then the returner quickly moved that way to catch the ball. Instincts kicked in and he lowered his shoulder with the ball carrier now in his path.
Wasn't great. Wasn't dirty either.