Clancy, the Maryland-based author, and his partner, movie producer and businessman James Robinson, extended an offer to Mackey on Wednesday after several months of discussions. In addition to being an investor, Mackey also would be a candidate for general manager, Robinson said.
Mackey was not immediately available for comment, but he told The Evening Sun, "I'm elated, but will go back home to California, talk with friends I respect for their knowledge and make a decision."
Clancy was introduced to Mackey by David Cohan, a lawyer who has helped Clancy with his NFL bid and who negotiated Mackey's player contract more than 20 years ago, Clancy said.
Mackey would bring to the group an insider's knowledge of football and football players, Clancy said. Mackey was the first president of the NFL Players Association, the union of football players.
"It's also relevant to say he's the best tight end who ever lived," Clancy said.
Mackey, now a sales marketing consultant living in Long Beach, Calif., retired from football in 1972 after 10 seasons, 331 receptions, 5,236 yards and 38 touchdowns. He played in five Pro Bowls and was inducted into the Hall of Fame this year.
He came to the Colts as a second-round draft pick from Syracuse University and played here until 1971, developing a reputation as a devastating blocker and someone who could run over tacklers after receptions. He ended his career with the San Diego Chargers.
Earlier this week, Leonard "Boogie" Weinglass, head of a rival ownership group, announced the addition of another former Colt, Joe Washington, to his investors. He said Washington, who is black, might serve as general manager if Weinglass were to get a team.
The NFL has not had a black general manager.
Among the five cities competing for an NFL team, only St. Louis has a black investor: former Chicago Bears great Walter Payton.
Florida businessman Malcolm Glazer also is seeking to own a team in Baltimore.