The San Francisco 49ers lost a major piece of their defensive puzzle in the third quarter of their Sunday Night Football win over the New England Patriots, as defensive end Justin Smith went down with an elbow injury. He played one more down before exiting the game for good.

On Monday, Smith will undergo an MRI to determine the extent of the injury. And as much as he is hurting, his absence hurts just as much.

Smith's presence on the opposite end has allowed the other Smith, Aldon, to flourish as a havoc-wreaking sack specialist. Without Justin on the other side, Aldon didn't get nearly the amount of pressure the Niners have become accustomed to seeing. If Justin is out for some time, it could have a ricochet effect on the best defense in the NFL.

For the Patriots, they lost starting cornerback Alfonzo Dennard to a knee injury and his replacement, Kyle Arrington, gave up Michael Crabtree's 38-yard touchdown catch in the fourth quarter.