Ron Rivera was declared cancer-free after a checkup Thursday.

Rivera, who announced on Aug. 20 that he had squamous cell cancer, tweeted thanks Thursday for the support he received during his treatment and recovery.

"Thank you everyone for your prayers, letters, texts & notes of encouragement & support. It truly made a difference in my treatment & recovery!#RiveraStrong @WashingtonNFL," he wrote.

The Washington Football Team coach needed to undergo seven weeks of treatment for the cancer during the season, which included three rounds of chemotherapy and proton therapy five days a week.