Michael Strahan, who played seven of his 15 seasons under Fassel, mourned his former coach Tuesday on Good Morning America.
"Just a great man, great coach," Strahan said. "And, he will be missed. But, I was definitely shocked this morning to find out this news and I just wanted to send my love and condolences to his family."
The 1997 NFL Coach of the Year started his professional coaching a career as a quarterbacks coach for the Giants in 1991. He served as Giants offensive coordinator in 1992.
Fassel went 10-5 in his first season. He led the Giants to a 12-4 record and a Super Bowl appearance in 2000-01. The Giants fired Fassel at the end of the 2003 season.
Fassel worked as the Baltimore Ravens offensive coordinator from 2004 through 2006. He ended his coaching career with a four-year tenure as head coach of the Las Vegas Locomotives of the United Football League.
Fassel served as a coordinator, assistant coach, positions coach and head coach at the collegiate level from 1974 through 1989.
He played collegiately at Long Beach State and was a seventh-round pick by the Chicago Bears in the 1972 NFL Draft.
Fassel also spent time with the San Diego Chargers and Houston Oilers. He ended his playing career after brief tenures with the Canadian Football League's Toronto Argonauts and the Hawaiians of the World Football League.