What a devastating sequence of events for the Browns, who lost a touchdown — and gave possession back to Kansas City — after receiver Rashard Higgins fumbled the ball out of the back of the end zone.

Higgins, who had caught a 23-yard pass on the previous play, again got open, and Mayfield found him. But as Higgins neared the goal line, reaching out with the ball toward the right pylon, in swooped Chiefs safety Daniel Sorenson, whose hit dislodged the ball. The rules state that if a team fumbles the ball and it goes out of the opponent’s end zone, the play results in a touchback.

Video replay confirmed the call on the field, and instead of a Cleveland touchdown drawing the score to 16-9, pending the extra point, the Chiefs assumed possession on their own 20-yard line. Making it worse for Cleveland was that the former N.F.L. official Gene Steratore, speaking on the CBS broadcast, said Sorensen should have been penalized for illegal use of his helmet. But that call is not reviewable, Steratore said.

That was of little solace to Browns fans, who have a long history with unfortunate postseason plays. According to ESPN Stats and Information, Higgins’s fumble was Cleveland’s first lost fumble in the playoffs inside the 10-yard line since Earnest Byner’s infamous fumble at the 1-yard line against Denver in the 1987 A.F.C. championship game.