Derby fans - excitedly chanting about promotion before the match - were soon silenced by an incredible performance from Sven Goran-Eriksson's Leicester.
Yet another strike from in-form midfielder Andy King and a Steve Howard penalty were more than enough to send the Rams crashing back down to earth after an impressive run of form that has seen them climb to fourth before today's clash.
Eriksson made just one change to the team that played out a 2-2 draw with strugglers Sheffield United on Wednesday night, with Steve Howard impressing enough to earn his place in attack ahead of Martyn Waghorn.
City were clearly fired up for the match and out played the Rams for virtually the whole afternoon and will feel they were unlucky not to win by more goals as they constantly battered the Derby goal.
An early lead seemed to settle the Foxes and they continued to press high up the pitch.
When Richie Wellen's sent an inch perfect ball into the path of Andy King on 13 minutes, there was no doubting the conclusion as the midfield ace placed his shot low past 'keeper Frank Fielding.
The Foxes grew ever more confident as the action unfolded. A confident and steady back four allowed the midfield trio of King, Wellens and Abe to control proceedings at the heart of the team whilst Darius Vassell's pacey and tricky runs always looked a threat but the main problem facing the Rams defence on the day was the powerful presence of Super Stevie Howard.
The veteran striker - a former Derby talisman - lead by example in attack and his desire to score against his old club was clear to see all afternoon. And, his efforts were rewarded midway through the second half when Kyle Naughton was brought down in the 18-yard-box to give the referee the easiest of decisions.
Howard showed the same leadership and confidence as he did late on in the Sheffield United match - smashing the ball home. The Foxes faithful were sent into a state of ecstacy. and '2-0 on your big day out' began to ring out around the ground as Eriksson's men went searching for more goals.
Lloyd Dyer - earning a reputation as a very useful impact sub - could have scored a brace when he replaced Vassell on the hour mark but for a couple of fine saves from Fielding, who was saving the Rams from further embarassment as they continued to crumble.
Two goals and another clean sheet for Eriksson's flying Foxes - all in front of a buzzing Walkers Stadium has made this a day to remember.
The win sees the Foxes climb two places into 15th whilst Derby's first loss in four matches means they drop a place to fifth.