Mike Pereira expects officials to struggle to handle the NFL's rule changes regarding defenders lowering their heads for contact.

Pereira, the league's former vice president of officiating, discussed the topic with Sirius XM NFL Radio.

"I think it's going to be impossible to officiate," he said. "You'll see the same things happen with this as we've seen with the crown-of-the-helmet rule: very few calls. I think most of it will be taken care of after the fact with potential fines."