The Chiefs opened as 3-point favorites over the Patriots at the SuperBook at Westgate Las Vegas.
New England had been favored in its past 12 playoff games, a streak that dates back to the 2013 AFC Championship Game. The Patriots were road underdogs against Peyton Manning and the Denver Broncos and lost 26-16 in that game.
If the line holds, this season's AFC Championship Game will mark only the seventh time in 39 playoff games that the Patriots will be underdogs with head coach Bill Belichick and quarterback Tom Brady, according to ESPN Stats & Information research. New England is 3-3 straight-up in its previous six playoff games as an underdog.
The Patriots were 4-point favorites when they hosted the Chiefs on Oct. 14. New England won 43-40.
The over/under opened at 59 in next week's rematch, but had ticked down to 57.5 by Sunday afternoon.
The Saints, the top seed in the NFC and the consensus Super Bowl favorites at sportsbooks, beat the Rams, the No. 2 seed, 45-35 in New Orleans on Nov. 4.
The over/under in next week's NFC Championship Game opened at 57.
The current Super Bowl line at the Westgate is NFC -1.5 vs. AFC.