Ten-man Derby lost 3-0 at Reading which extended their winless run in the Championship to six matches.
Derby lost defender Scott Malone to a red card for a foul in only the fourth minute, with Charlie Adam slotting in the subsequent penalty for Reading.
Although Derby played well with a numerical disadvantage, they could not force a first-half equaliser.
The visitors battled bravely after the break but fell further behind in the 58th minute when Lucas Joao slotted in his fourth goal for Reading this season.
Yakou Meite added a second spot-kick for the home side near the end after Joao had been brought down in the area.
Derby had not won in five matches, picking up just two points, and had lost their five previous away games - without scoring a goal.
Reading had won only once in six outings after new manager Mark Bowen's tenure had started with a four-match unbeaten run.
Derby got off to the worst possible start when they conceded a penalty after just four minutes and had Malone sent off in the same incident.
Joao released Meite, who was pushed over by Malone as he was attempting to go past goalkeeper Ben Hamer.
Referee Michael Salisbury deemed it was a straight red and Adam slammed in the spot kick, in the fifth minute, for his first goal for the club.
Derby manager Phillip Cocu immediately sacrificed striker Chris Martin, the former Reading loanee, for substitute midfielder Max Lowe.
It drew a swift response, with Tom Lawrence cutting in from the left flank and firing in an angled drive that beat home keeper Rafael and thudded against a post.
Reading then dominated for long periods, mostly through the expert passing and prompting of Adam.
But they struggled to create any clear-cut chances and Derby could have levelled on the counter only for Jason Knight to shoot narrowly over.
Reading quickly regained momentum, with Sam Baldock going close from an incisive Ovie Ejaria pass.
Meite also tried his luck from 25 yards out but was marginally off target.
Again Derby persevered on the break, with Rafael saving well from a fiercely struck shot from Knight.
Reading opened the second period more aggressively, with Hamer having to react smartly to deny Baldock.
Derby reacted positively, with Krystian Bielik shooting wide.
But Reading increased their 13 minutes into the half, when substitute John Swift crossed to the near post and Joao tucked home past Hamer.
Derby never gave up and Knight almost reduced the gap when his 20-yard drive thumped against the home crossbar.
Reading made it 3-0 four minutes from time when Craig Forsyth brought down Joao in full flight and, this time, Meite drilled in the resultant penalty.
What the managers said...
Reading's Mark Bowen: "When you're playing against 10 men, it can be a difficult situation. Teams can flip the way they go about the game. At half time, maybe I wasn't happy about the situation, but the players weren't happy about the situation and what they had produced since the goal.
"Derby probably had too many chances but I thought that when we came out for the second half, we were patient and then moved the ball quickly. But we didn't risk it by trying to cut through them every time. We brought them on to us and created those spaces to play in. I thought that we did that. It was the perfect start for Christmas week."
Derby's Phillip Cocu: "With all the cards, I saw it in a positive way. It meant that we reacted together as a team. There were some moments when there were some provocations from some [Reading] players after they were 2-0 up. They had some tricks.
"It's their game, they do it. But we showed what we stand for, that you don't mess with us. You have to stand up for yourself sometimes and that's when you get a booking."