The 41-year-old Favre retired in the offseason after a 20-year career and lives in Hattiesburg. Irsay sent a tweet on Sunday saying "Brad, I'm in Hattiesburg ... is it right or left at the Firechief?"
Favre's longtime agent Bus Cook said he hadn't spoken with the quarterback in a few days, but the "last time I saw him he was on his tractor mowing the back forty."
Through a spokesman, Colts' general manager Chris Polian declined comment on Irsay's tweet.
Though Favre has repeatedly said he's retired during the offseason, any Colts' interest would make some sense. Peyton Manning had neck surgery in May and hasn't played in the preseason, casting doubt on his 227 consecutive games streak.
That's a scary proposition for the Colts, who have little experience behind him.
"I certainly want to be out there, and it's hard to keep track of the hours I've spent in rehab," Manning said on Saturday. "I was short-changed a little bit by the lockout and I'm going to need every bit of the next two weeks, and then I can give you more of an update with where I am."
Curtis Painter has started both preseason games, completing 8-of-16 passes for 95 yards with no touchdowns and one interception. In Friday night's 16-3 loss to Washington, Painter managed only one first down and couldn't get the offense past its 29 despite playing the entire first half.
He hasn't played in a regular season game since 2009.
On Saturday, Irsay acknowledged on his Twitter feed that the Colts might not have their four-time MVP quarterback at the start of the season. Manning signed a five-year, $90 million contract in July after the 4½-month lockout ended.
Favre is a three-time MVP and has thrown for more than 71,000 yards and 500 touchdowns, winning a Super Bowl with the Green Bay Packers along the way. But the famous gunslinger began to show some serious wear in 2010 with the Minnesota Vikings, throwing for 2,509 yards, 11 touchdowns and 19 interceptions in an injury plagued season.
He also was hounded with allegations that he sent lewd photos and messages to a game-day hostess when both worked for the Jets in 2008, and was fined $50,000 by the NFL for failing to cooperate with the investigation.
But with Favre, anything seems possible. He retired with the Packers in 2008 and New York Jets in 2009 before deciding on a return. Favre has kept a low profile during the offseason, saying at a football camp at the University of Southern Mississippi that he wasn't sure of his future plans, though he insisted he was done playing football.