Vice chairman Bill Polian and his son, general manager Chris Polian, became the first casualties of the Colts' 2-14 season, getting the ax in what Irsay said was the best move for the franchise going forward.
"It was difficult," Irsay said at an afternoon press conference. "(But) it was time."
The Colts won eight division titles and made 11 playoff appearances with Polian in the front office and Manning on the field. Their run included nine straight years of double-digit wins, but collapsed this season with Manning unable to play because of a neck injury.
"Fourteen years is a long time," Irsay said. "In the end, I thought this was the best move for the franchise."
Chris Polian had been the Colts' general manager since 2009. Head coach Jim Caldwell was not fired.
Indianapolis lost its first 13 games of the season, then won two straight, but secured the draft's top pick after a 19-13 loss to Jacksonville on Sunday.
Of course, speculation about what the Colts would do with a No. 1 pick has built all season long. They could select Stanford quarterback Andrew Luck, seen as the draft's top prize, or trade the pick away
"We're moving into exciting times," said Irsay.