The Broncos take on the Colts in their first match since their emphatic defeat at the hands of the Seattle Seahawks in the Super Bowl in February.
Harris has admitted that Luck has provided a tough physical challenge like Roethlisberger when he has faced the quarterback in the past.
He told the club's official website: "I'm treating Andrew Luck like Big Ben. When you're playing Roethlisberger, you can't tackle him low. You have to tackle him high, and tackle the ball, because he's so strong.
"So we know with Andrew Luck running around, we've got to plaster -- and 'plaster' means we've got to lock onto our guys immediately when we see him out of the pocket, because it's going to happen."
The Broncos face the Colts at Sports Authority Field tomorrow night.