"I think they do a great job of mixing up coverages and disguising coverages," Luck said. "It's hard to get a beat on what they're doing."
Luck pointed to how the Patriots have dealt with multiple injuries in their secondary, especially at safety.
"They're banged up here and there, but they do a great job I think of getting the job done," Luck said. "It will be a very tough test for us."
The Patriots run defense was one of the league's best through the first half of the season, but hiccuped last Sunday against the Buffalo Bills, allowing 162 yards on the ground.
On the whole, Luck said he still believes that containing the Patriots' defensive line is a difficult task.
"I think their front four is incredibly stout. (Vince) Wilfork is one of the best nose tackles in the league," he said. "Their two very good edge rushers on the side. They do get to the quarterback, and even if it's not a sack, they harass (you), force the quarterback to throw, force the quarterback out of the pocket.
"That will be the focus all week," he added, "and I'm sure our line will do a great job and it will be a great test for them."