Hansel Ochieng struck the lone goal as Nzoia Sugar stunned champions Gor Mahia 1-0 in a thrilling SportPesa Premier League match at Mumias Sports Complex on Wednesday.
The shock defeat took some gas off Gor's march towards an unprecedented 18th Premier League title - their third in row and sixth in seven years.
Fresh from winning the perceived title decider against second-placed Sofapaka by two unanswered goals over the weekend, Gor were undone by a 34th-minute goal scored by Hansel Ochieng.
K'Ogalo, considered champions in waiting with four games remaining till the end of the 2018/2019 league season, face arch-rivals AFC Leopards on Sunday in the Mashemeji derby at the Moi International Sports Centre, Kasarani.
Gor remain on top on 56 points, 10 ahead of second placed Sofapaka who have played one more game. Bandari, in third place, are 11 points behind Gor after 29 rounds of matches.
In other results, Zoo Kericho battled from a goal down to beat visiting Western Stima 2-1 at the Kericho Green Stadium while high-flying Sony Sugar edged hapless Kariobangi Sharks 2-0.
Nzoia Sugar 1-0 Gor Mahia
KCB 1-0 AFC Leopards
Kariobangi Sharks 0-2 Sony Sugar
Zoo Kericho 2-1 Western Stima