John Obi Mikel and Oscar scored a goal each in five second-half minutes, as Chelsea knocked a resurgent Derby County out of the FA Cup at the iPro Stadium.
The Rams put in a performance to be proud of as they gave the former Champion’s League winners a great game, and weren't to be outplayed by some of the visiting international stars in a strong Chelsea line up.
Derby matched the Europa League winners in a first-half that required the Rams' back-four, lead by captain Jake Buxton, to be at their very best as Samuel Eto’o, Michael Essien and Oscar had several chances to put the visitors in front.
Oscar looked to be the Blues' biggest threat, shooting narrowly wide from distance and sending a free-kick inches over the crossbar, after Michael Essien had been tripped by John Eustace.
However, it was not all defensive duty for the Rams, as they refused to be intimidated, and carved a number of opportunities for themselves with Jamie Ward and Eustace calling Mark Schwarzer into action.
In the second-half, however, Chelsea stepped up a gear and demonstrated their Premier League quality, piling pressure on the Rams, who defended bravely but were ultimately unable to keep the visitors out.
Chelsea decided the tie, netting twice in the space of five minutes, firstly through Mikel’s 66th minute header and then in the 71st minute when Oscar’s piledriver of a shot found its way past Lee Grant.
Derby rallied in the last ten minutes and mounted some pressure of their own, but Chelsea’s defence stood firm as Derby bowed out of the competition.
The Rams endured a lot of pressure in the opening ten minutes of the game but were well organised at the back and defended well, keeping the visitors at bay and restricting them to efforts from long range.
Steve McClaren's men came into the game more and more over the next ten minutes, passing well and creating a number of chances themselves.
A great low cross from Craig Forsyth almost found Ward at the near post, but the Blues were able to clear the ball away and minutes later, Simon Dawkins hit a powerful shot from around 25-yards that rose over Schwarzer’s goal.
Chelsea begun to threaten again with some superb passing in the middle of the pitch and the home fans’ hearts were in their mouths when Samuel Eto’o muscled Michael Keane off the ball and went clear through on goal only to be stopped by some excellent defending by skipper, Buxton.
After Eustace tripped Essien, Oscar’s curling free-kick from 25-yards did not quote bend enough to find the net, but the visitors were piling on the pressure and the Brazilian threatened to break the deadlock again in the 37th minute with a super effort from 20-yards that went inches wide of Grant’s right post.
Derby came right back at Chelsea shortly after when Eustace won the ball in midfield and tried his luck from just outside the are, but his effort was straight at Mark Schwarzer who gathered the ball comfortably.
However, Chelsea were on the front foot again in the last five minutes of the first-half and with almost the last kick of the period, Ramires hit the far post with a great effort from the edge of the area.
Chelsea started the second period strongly and continued to create chances with the game predominantly being played in Derby’s half, with Oscar remaining a real threat.
But Derby remained resolute in defence and had a great chance to score themselves in the 52nd minute when a counter attack saw Will Hughes tripped on the edge of the Chelsea area, but Jamie Ward’s free kick was too high and Schwarzer was able to watch the ball sail over his crossbar.
Chelsea then took control of the game and the pressure eventually told in the 66th minute. Willian whipped in a free-kick from the left, which was met by the head of Mikel, who powered the ball home from close range.
Five minutes later Oscar, who had been a thorn in the Rams’ side throughout the contest, created space for himself in the box and doubled the visitors’ lead with a swerving effort that powered past Grant, who could only palm the ball into his own net.
Fernando Torres had two golden opportunities to extend the Blues' lead. The first chance ended with the Spaniard getting the ball stuck under his feet after rounding Grant, and the second time, drawing a great save out of the Rams ‘keeper.
And minutes later, Ramires had a shot from around 25-yards that took a deflection before arcing onto the cross bar, before David Luiz's shot from the resulting corner, was headed clear by Chris Martin.
Derby rallied in the last ten minutes and almost got themselves back into the game when Conor Sammon showed great strength to hold off three Blues players and play a neat through ball to Martin, who forced Schwarzer into a good save low down at his near post.
In the dying moments, substitute, Mason Bennett, controlled the ball well and shot narrowly wide of Schwarzer’s left post, but Derby’s efforts were in vain as the Premier League giants knocked the Championship promotion contenders out of the F.A. Cup.
Derby County: Grant (GK), Wisdom, Forsyth, Eustace (Bennett 70'), Keane, Buxton, Hughes, Hendrick, Martin, Ward (Sammon 69'), Dawkins (Bailey 83'),
Subs: Legzdins (GK), Freeman, Whitbread, Cissé.
Chelsea: Schwarzer (GK), Azpilicueta, Cole, Mikel, Cahill, Luiz, Ramires, Essien (Hazard 55'), Eto'o (Torres 64'), Oscar (Baker 87'), Willian.
Subs: Cech (GK), Mata, Terry, Kalas, Baker.