Brett Favre has been a bit of a good luck charm for the Kansas City Chiefs -- they're 2-0 when he's attended their recent Super Bowls -- but he can't make it to the big game this weekend ... and now, he's hoping that doesn't jinx Patrick Mahomes and Co.
The NFL legend tells TMZ Sports ... because of his close relationship with Andy Reid, he's previously gone out to two of K.C.'s three most recent SB appearances to give a championship pep talk to the team.
Both times, he said, they won ... so, naturally, Reid invited him out to Las Vegas this week to keep the streak going.
However, Favre says he's not going to be able to be in attendance this year -- and he's nervous about the juju it might bring to Chiefs Kingdom.
"Knock on wood!" the ex-Packers quarterback said.
Superstitions aside, Favre tells us he's super proud of what Reid has accomplished since the two worked together in Green Bay way back in the 1990s ... telling us he could see even then that Reid had this in him.
In fact, he says he's never seen Andy happier ... and he can't fathom Big Red retiring after Sunday no matter what happens against the 49ers.
"He's enjoying -- maybe more so than any other time in his career -- what he's doing," Favre said. "He seems to be in a really good place."
While it seems Favre will be in KC's corner by the time kickoff rolls around at Allegiant Stadium ... he did offer some big praise for Brock Purdy too -- and he even had some words of advice for the young Niners QB heading into the game as well.