Sullivan (back) did not participate during the Panthers' practice Thursday.
Sullivan appears to have picked up a back injury after logging a full practice Wednesday, though the exact nature and severity of this issue are unclear. The third-year tight end recorded his lone catch of the season in Week 2, and he has played 40 of his 47 total snaps on special teams over three games. Sullivan will have once more practice to improve his status before Sunday's game against San Francisco.