Match ends, Reading 0, Derby County 1.
Derby claimed a second away win in as many games as they beat 10-man Reading in the Championship.
Tom Ince scored the game's only goal midway through the second half after Chris Martin threaded a ball through the home defence.
Reading striker Orlando Sa was shown a straight red card for an incident off the ball with Jason Shackell on the stroke of half-time.
The defeat ends Reading's seven-game unbeaten run in all competitions.
Paul Clement's Derby side, who failed to win their first five league games before a 2-1 away win at Preston on Saturday, were made to work for the three points.
Reading, full of confidence after a resounding 5-1 home win against Ipswich on Friday, had the better of the early chances.
Nick Blackman and Oliver Norwood went closest before half-time as Scott Carson was forced to tip long-range efforts behind.
Derby were limited to a header from Richard Keogh, which was easily held by Jonathan Bond.
But, moments before the break, Sa was dismissed as he tangled with Shackell after the ball was cleared.
The Portuguese striker, who netted a hat-trick against Ipswich, appeared to headbutt Shackell and referee Andy Davies had no hesitation in sending him off.
The numerical advantage took time to tell for the visitors until Ince found space from Martin's precise pass.
Reading pushed hard for an equaliser, but the visitors' disciplined shape off the ball meant substitute Hal Robson-Kanu's tame header over from a corner and Chris Gunter's lashed volley was the closest they came.
Reading manager Steve Clarke:
"I haven't seen the red card. One or two people said it was a bit silly, others said it was a bit soft. Until I actually get a look at it again, it's hard to judge.
"It certainly changed the game as 11 against 11, one good team was trying to win it, the other half-decent team was trying to make sure it got a point from the game.
"It's harsh to judge us on tonight as we lost against a good team, who will certainly finish in the top six, and we handled them well."
Derby County head coach Paul Clement:
"A brilliant response from the players after a difficult start to the season. We hadn't been playing that badly before, but we just weren't picking up the results.
"The sending off is a big turning point, it changed everything. I hadn't seen it, but at half-time Jason Shackell said the head was put on to him in a coming together and the referee's seen it and quickly made the decision.
"You come to a place full of confidence after a big home win and we had to be at our best to control the attacking threat. We had to be patient as playing against 10 men isn't easy."
- 2GunterBooked at 90mins
- 18TshibolaBooked at 24minsSubstituted forMcClearyat 80'minutes
- 21QuinnSubstituted forRobson-Kanuat 68'minutes
- 10SáBooked at 45mins
- 7VydraSubstituted forWilliamsat 63'minutes
- 26Al Habsi
- 14ShackellBooked at 45mins
- 8HendrickSubstituted forBentat 61'minutes
- 15JohnsonBooked at 62mins
- 18ButterfieldSubstituted forHansonat 75'minutes
- 23InceSubstituted forWeimannat 84'minutes
- Andy Davies
- Shots on Target
Second Half ends, Reading 0, Derby County 1.
Attempt missed. Chris Gunter (Reading) left footed shot from the centre of the box is high and wide to the right. Assisted by Garath McCleary with a through ball.
Corner, Derby County. Conceded by Hal Robson-Kanu.
Oliver Norwood (Reading) is shown the yellow card for a bad foul.
Richard Keogh (Derby County) wins a free kick in the attacking half.
Foul by Oliver Norwood (Reading).
Attempt missed. Hal Robson-Kanu (Reading) header from the centre of the box is too high. Assisted by Oliver Norwood with a cross following a corner.
Corner, Reading. Conceded by Craig Forsyth.
Attempt blocked. Danny Williams (Reading) right footed shot from outside the box is blocked. Assisted by Hal Robson-Kanu.
Chris Martin (Derby County) wins a free kick in the defensive half.
Foul by Jordan Obita (Reading).
Substitution, Derby County. Andreas Weimann replaces Tom Ince.
Corner, Reading. Conceded by Jason Shackell.
Attempt blocked. Garath McCleary (Reading) right footed shot from outside the box is blocked. Assisted by Oliver Norwood.
Substitution, Reading. Garath McCleary replaces Aaron Tshibola.
Attempt missed. Craig Forsyth (Derby County) left footed shot from the left side of the box is just a bit too high. Assisted by Bradley Johnson.
Attempt missed. Nick Blackman (Reading) left footed shot from outside the box is too high from a direct free kick.
Foul by Jamie Hanson (Derby County).
Nick Blackman (Reading) wins a free kick in the attacking half.