ASHBURN -- Ron Rivera missed Tuesday's Washington Football Team practice as the head coach was undergoing treatment for squamous cell carcinoma. 

Rivera revealed his cancer diagnosis last month in a private meeting with the team and later to the media. In his absence, defensive coordinator Jack Del Rio will act as interim head coach. 

Washington cut its roster from 80 players down to 53 over the weekend, and now the team prepares for its first game of the year on Sunday against Philadelphia. 

It's unclear what time Rivera will miss to recover from treatment. Much of that will be determined by how the coach feels.