The staff, wearing "Rivera Strong" shirts, cheered along the hallway before the coach rang the ceremonial bell.
Rivera announced in August that he was diagnosed with squamous cell carcinoma in a lymph node and required treatment for seven weeks. Per John Keim of ESPN, he now only has follow-up appointments and scans remaining.
"The fatigue, I told my wife it's like having a 300-pound gorilla on your back," Rivera said of the treatment.
The 58-year-old has remained on the sidelines for Washington, leading the team to a 25-3 win over the Dallas Cowboys on Sunday at FedEx Field.