The Falcons have struggled against the run this season ranking 30th in the NFL in rushing defense and will go up against Lacy, who has ran for 800 yards this year at an average of four yards an attempt.
"The way we've been playing run (defense the) last couple weeks, it's a big concern," Smith told the Atlanta Journal-Constitution.
"Green Bay had made a concerted effort to run the football this season. We will see a big, strong running back this week who we have to put multiple pads on. We have to tackle much better than we did Sunday."
The Falcons are 3-9 in their season going into week 14.