Castro-Fields (shoulder) has been ruled out ahead of Sunday's game against the Cowboys, John Keim of ESPN.com reports.
Castro-Fields drew the first start of his young career in Week 17, but he sustained a shoulder injury that's held him out of practice all week, so it's no surprise that he won't suit up Sunday. The Commanders' secondary will be extremely thin in Week 18, as Castro-Fields is one of three cornerbacks to already be ruled out.