With the result, the home side from Prague suffered their first-ever competitive defeat under new manager Lars Friis and lost at home for the first time since last May.
As expected, it was the Spartans who stormed into the match with great vigour. They managed to get the ball into the net after only four minutes, but Lukas Haraslin was offside on his run and his shot could not stand. However, the home side made up for it in the 13th minute.
Peter Vindahl's surgically precise kick found Veljko Birmancevic running on the right wing, who centred to Olatunji from the first, and the latter successfully finished off the wonderful move of the side in red with a superb header.
They dominated the rest of the opening period at a rainy Epet Arena, but despite their superiority, they went into the dressing rooms with only the narrowest of leads.
After returning to the pitch, the pace of the match dropped slightly and the first major upset came after 10 minutes of the second half.
Matej Rynes found himself untouched by anyone in the centre of the pitch, ideally prepared the ball and practically from a step he hit it with his left foot into the crossbar so forcefully that it was still shaking for a few seconds.
Shortly before the start of the last twenty minutes, an Olomouc cross made it to Matej Mikulenko, from whom it bounced to Muritala to score, and despite Sparta's dominance so far, the game was level.
To make matters worse, in the 78th minute, Sigma's Nigerian striker took a shot at Vindahl, who flicked the ball to substitute Jan Fiala, who then silenced the crowd for good.
Then, after a throw-in near his own penalty area, Jaroslav Zeleny mis-controlled the ball, offering it to Filip Zorvan, who finished into the empty net to shock the Spartans for the third time. The home team added a consolation goal through Ermal Krasniqi late on.
No more goals were scored and Olomouc took a sensational three points away. Sparta must now prepare for a busy week when they first play in the Champions League in Stuttgart and then play the Prague derby against Slavia. Sigma will try to build on their surprise triumph at home against Bohemians.