From Tom Orsborn:
Wade Phillips said Spencer was held out for precautionary reasons. He was replaced by second-year player Victor Butler.
"He had a great day today," Phillips said of Butler. "He started out slow (at camp) but then the last four to five practices he's really practiced well and rushed the passer like we thought he could."
Wide receiver Dez Bryant, defensive lineman Sean Lissemore, offensive lineman Montrae Holland and safety Patrick Watkins will all sit out Sunday's game with injuries.