Legendary sportscaster Gifford, died of natural causes at his Connecticut home that he shared with wife Kathie Lee, on Sunday, aged 84.
Taking to Instagram on Monday, Cassidy, 22, told her followers: “Very few people are blessed enough to call their father a legend, and an even smaller number are able to share that notion with the rest of the world.”
She added: ” Yesterday, I lost my best friend… His kindness was infectious, and his grace, beyond compare .. And despite the worldly passing of an incredible man, I undoubtedly know heaven gained one stud of an angel.”
Also paying an emotional tribute on Monday was Hoda Kotb, who broke down in tears on the Today show.
Talking about her co-host and Cassidy’s mother Kathie Lee Gifford, Kotb, 51, said: ” She is remarkably strong, I’m in awe of her even today.”
The family released a statement to PEOPLE announcing the football star’s death on Sunday.
The statement reads in part: “We rejoice in the extraordinary life he was privileged to live, and we feel grateful and blessed to have been loved by such an amazing human being.”