Derby's miserable away form in the npower Championship continued as they failed to recover from a dismal start at promotion-chasing local rivals Leicester.
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England Under-21 international Martyn Waghorn set up Zak Whitbread for Leicester's opener, added a second with a cool side-footed finish and could have scored three more in an embarrassingly one-sided opening half-hour.
The visitors belatedly sprung into life and pulled a goal back through Theo Robinson's 38th-minute half-volley.
Leicester were not to be denied, though, and wrapped up an eighth home win of the campaign - and fifth successive league win over County - through two late goals from substitute David Nugent.
Nigel Pearson's men move up to third in the table as a result of their victory, while Derby, such a formidable force at Pride Park, have now lost their last four on the road and lie 16th.
Each side showed two changes from their midweek assignments. Paul Konchesky and Anthony Knockaert were restored to Leicester's line-up, while Derby brought in James O'Connor and Jeff Hendrick in place of injured duo Gareth Roberts and Craig Bryson.
The excellent Waghorn was at the heart of the action as Leicester initially threatened to run riot, creating eight presentable chances before their opponents could muster a noteworthy attempt on goal.
Whitbread registered his maiden goal for the Foxes when heading home the forward's outswinging corner in the sixth minute.
Waghorn then forced a save from Adam Legzdins with one free-kick and rattled the crossbar with another before hitting the target again with an acrobatic volley.
Leicester soon added a deserved second when Knockaert capitalised on an error from O'Connor and picked out Jamie Vardy in the box. An unselfish lay-off to Waghorn followed and the game's outstanding player finished with ease.
Some atrocious defending enabled Vardy, who had earlier fired wide, and Knockaert to bring further stops from Legzdins, but Derby eventually woke from their slumber and dominated the remainder of the first period.
The Rams were rewarded for their improvement when Robinson latched onto a cross from Michael Jacobs and took a touch before stabbing a powerful finish beyond Kasper Schmeichel.
Conor Sammon and Robinson were subsequently denied by Schmeichel, before Lloyd Dyer got the hosts going again in the 57th minute with a fine run and shot that was beaten away by Legzdins at his near post.
Derby continued to pose problems at the other end, prompting a double change by Pearson that saw Nugent and Ben Marshall introduced in place of Vardy and Dyer.
After Waghorn had seen an effort deflect on to the underside of the bar via the body of Legzdins, the substitutes combined to settle home nerves with 16 minutes remaining.
Marshall delivered a pinpoint cross from the left, leaving Nugent with a simple close-range header.
That knocked the stuffing out of Derby and there was time for Nugent, who also had a goal disallowed, to rub salt into the Rams' wounds with an 89th-minute half-volley into the top-right corner.