Manning has said in the past that all he wanted to do was finish his career in a Colts uniform, but an injured neck forced him to miss all of the 2011 season.
"I can't tell you what an honor it is to go start-to-finish with the same organization here in Indianapolis. That is something I have always wanted to do as a rookie coming out," Manning said after signing a five-year, $90 million contract in July. "Of course, you never know if that is possible, but after yesterday it is official that I will be an Indianapolis Colt for my entire career. I will not play for another team. My last down of football will be with the Colts, which means a great deal to me."
But things have changed since last summer. Now it looks like the NFL's only four-time MVP, and a former Super Bowl champion, won't be wearing No. 18 for Indy.
With a $28 million bonus payment due Thursday to Manning, his neck problems, and the fact that the Colts own the No. 1 pick in April's draft, the Colts seem to have deemed it too risky and too pricey to keep the longtime franchise quarterback, who will turn 36 later this month.
The twists and turns of a public debate between Manning and Irsay, who have been friends for more than a decade, created the sense the two had been fighting. Irsay twice issued statements to deny a rift.
Still, with the Colts in full rebuilding mode, Irsay has been expected by many to play for the future and let Manning try to chase a second Super Bowl ring somewhere else.
The Colts are expected to take Stanford quarterback Andrew Luck with the first pick in April's draft.
Manning's impending departure marks the end of a remarkably successful era that included the 2006 league title.
He started every meaningful game for 13 seasons in Indy, 227 straight including the playoffs, and took the Colts from perennial also-ran to one of the NFL's model franchises.
In the two decades pre-dating his arrival, the Colts won 116 games, one division title and made the playoffs three times. With Manning taking snaps, the Colts have won 150 games, eight division titles, two AFC championships and the franchise's first Super Bowl since moving from Baltimore in 1984.
Indy broke the league record for most regular-season wins in a decade (115), tied Dallas' league record for most consecutive playoff appearances (nine) and the success changed Indy from a basketball town to an NFL town.
Manning is one of four players with more than 50,000 yards passing, one of three with more than 350 touchdown passes and one of two quarterbacks with more than 200 consecutive starts. The only non-active quarterback with a rating higher than Manning's 94.9 is Hall of Famer Steve Young (96.8). He broke all of the franchise's major career passing records, previously held by Hall of Fame quarterback John Unitas, and he may not be finished.
In 2009, the star QB had the Colts on the cusp of history with a 14-0 start.
It's been mostly bad news ever since. The Colts pulled their starters against the New York Jets and lost the final two games that season. Indy then wound up losing to New Orleans in the Super Bowl. During the offseason, Manning had the first of his neck surgeries.
Then, after making an early playoff exit in the 2010 season, Manning underwent another neck surgery to repair a damaged nerve that was causing weakness in his throwing arm.
But when the nerve did not heal as quickly as anticipated, Manning had two vertebrae fused together in September, a surgery that forced him to miss the first game of his career. There are still questions about how strong Manning's arm is.
Yet he has repeatedly insisted he plans to play football again next season.
"My plan hasn't changed," Manning said during Super Bowl week. "I'm on track with what the doctors have told me to do, and I'm doing that. I'm rehabbing hard."
The question is where might Manning land if he is no longer a Colt.
Arizona, Miami, Tennessee and the New York Jets have all been rumored as possible spots, and Manning's former longtime offensive coordinator Tom Moore did work with the Jets as a consultant less season.
It's still possible, however unlikely, that Manning could return to Indy for a lower price if he can prove he's healthy.
"This isn't an ankle, it isn't a shoulder. Often times the NFL is criticized for putting someone out there at risk, and I'm not going to doing that," Irsay said in January. "I think he and I just need to see where his health is because this isn't about money or anything else. It's about his life and his long-term health."
Manning's career in Indianapolis
Yards TD Int
1998 • 3,739 26 28
1999 • 4,135 26 15
2000 • 4,413 33 15
2001 • 4,131 26 23
2002 • 4,200 27 19
2003 • 4,267 29 10
2004 • 4,557 49 10
2005 • 3,747 28 10
2006 • 4,397 31 9
2007 • 4,040 31 14
2008 • 4,002 27 12
2009 • 4,500 33 16
2010 • 4,700 33 17
Totals • 54,828 399 198