The San Francisco 49ers will have revenge on their minds when they face the unbeaten Kansas City Chiefs in a Super Bowl rematch on Sunday.

The Chiefs have beaten the 49ers in the Super Bowl twice in the past five seasons, including last February when San Francisco led in the fourth quarter.

It is something of a mantra in the NFL that past encounters count for nothing once the game gets underway, but Niners head coach Kyle Shanahan, who was in charge for both Super Bowl losses, knows it will be hard for his players to forget.