Barclays Premier League
Gareth Davis reports from Stamford Bridge
David Jones scored his first goal of the season but it was nothing more than a consolation for the Rams as Chelsea cruised to a 6-1 success.
It was just the result they needed to reignite their title hopes and they had eased to a 2-0 lead before half-time through Frank Lampard and Salomon Kalou.
Lampard fired in three more after the break to bring his evening's tally to four while Joe Cole added another before Jones struck from inside the box.
Robbie Savage was back in the Rams' line-up after missing out on the draw with Sunderland - returning in central midfield alongside Hossam Ghaly.
David Jones was among the substitutes, as was Dean Leacock, fit again after injury, while Derby's bench had an attacking feel to it with Robert Earnshaw and Tito Villa also among Paul Jewell's options.
And there was an appearance in the pre-match warm-up for teenage defender Miles Addison, who was kitted out and kicking in with the senior squad.
Chelsea, for their part, were able to list Didier Drogba and Andriy Shevchenko among their replacements, alongside Michael Essien, with Nicolas Anelka leading their line.
The home side almost found themselves in front with less than three minutes on the clock.
Salomon Kalou's challenge on Marc Edworthy sparked a break that ultimately saw Frank Lampard create space for himself inside the box - but he only struck the post.
The midfielder is normally so deadly from that distance and Derby almost made him pay as Edworthy's long ball released Kenny Miller, who span away from John Terry but blazed wastefully wide with more time than he realised.
Not surprisingly, the early football was coming from Chelsea, though another Derby break looked threatening as Miller crossed and Eddie Lewis couldn't quite stretch far enough inside the home box.
But the Rams were disrupted on the quarter-hour mark by an injury to Alan Stubbs, in fine form over recent weeks, who hobbled off with a calf problem to be replaced by Leacock,
Stamford Bridge was strangely quiet given the importance of the game for the home side, but on 26 the noise level went up.
Chelsea were awarded a penalty when Lampard, allowed to run un-checked into the Derby box, was caught by Leacock's challenge - and stepped up to open the scoring by sending Roy Carroll the wrong way from the spot.
The Rams were close to a quick equaliser however as Miller rose to meet Lewis's left-wing free-kick with a header that had Carlo Cudicini stretching to gather.
But Chelsea seemed to be playing in cruise control as they held on to the ball for long periods of time and made the Rams do the running.
Indeed, only some excellent blocks by Leacock, Moore and McEveley prevented them from having more clear sights of goal.
And the second duly arrived three minutes before the break.
Carroll was out to block well on the edge of his box, as Anelka chased Lampard's through-pass, but the ball rebounded out to Kalou who volleyed it calmly into an unguarded net from 25 yards.
Chelsea started to turn on the style and only a fine Carroll save prevented Michael Ballack from making it 3-0 seconds later.
Neither side made a change at half-time but once again Derby had a half-chance to give Chelsea something to think about when Lewis broke clear down the left but his cross was too near Cudicini.
At the other end Lampard and Anelka both went close, before Robert Earnshaw replaced Hossam Ghaly seven minutes in.
And when Joe Cole broke down the right on 56, Chelsea were soon three-up.
The England ace skipped past Pearson to the byline and pulled a low cross back for Lampard to tap in from close-range for his second of the evening.
Ballack threatened a fourth soon afterwards, while Derby's response was to replace Lewis with David Jones.
And it was four on 63. Anelka was released by a through pass and though Carroll saved his effort, the ball rebounded up for Joe Cole to roll home from just inside the box.
Seconds later Lampard drove home a fine low shot from the edge of the box to complete his hat-trick - and if that wasn't bad enough, on came Didier Drogba to replace Ballack.
Lampard was really enjoying his evening and took his personal tally to four, again from the edge of the box on 72 minutes after spinning past McEveley and firing home with his left foot.
Seconds later however, the Derby fans in the corner had something to cheer.
Miller's pass was deflected on its way into the Chelsea box and right in front of Jones, who slotted his shot clinically past Cudicini for his first goal of the season.
It was a moment that saw most of the Stamford Bridge crowd stand to applaud, though it had almost gone unnoticed that Chelsea also threw on Michael Essien and Andriy Shevchenko.
McEveley became referee Chris Foy's first caution of the night with five minutes to go as he caught Drogba out on the touchline.
But the last few minutes were played out at the pace of a training ground encounter with the game well and truly won by Chelsea.
CHELSEA: Cudicini, A Cole, Makelele (Essien 72), Carvalho, Lampard, J Cole (Shevchenko 74), Ballack (Drogba 65), Ferreira, Kalou, Terry (C), Anelka.
SUBS: Hilario (GK), Alex.
DERBY: Carroll, Edworthy, McEveley, Stubbs (Leacock 15), Miller (Jones 57), Lewis, Sterjovski, Moore, Pearson, Ghaly (Earnshaw 52), Savage (C).
SUBS: Price (GK), Villa.
ATTENDANCE: 39,447.
