Gates, Merriman are back on field

Posted by ESPN.com's Bill Williamson

SAN DIEGO -- Tight end Antonio Gates and linebacker Shawne Merriman are back on the field. Both ended the first half in the locker room. Gates has a hip contusion and Merriman left for undisclosed reasons. He has an existing left knee issue.

Defensive tackle Jamal Williams also missed two series for an undisclosed reason. He is also back.

San Diego's defense is tightening. Carolina ran and threw all over San Diego in the first half, but San Diego's defense made several key plays to hold the Panthers to three field goals.