Darren Byfield kept Sunderland's promotion drive on track as he put a huge dent in Reading's play-off dream and not for the first time.
Byfield made the crucial breakthrough in a tense match as he headed home George McCartney's cross 17 minutes from time, substitute Tommy Smith adding a second two minutes later.
And Byfield's goal would have served as a sour reminder of his extra-time strike to secure a play-off final win for Walsall over Reading at Cardiff's Millennium Stadium two years ago.
This year, Byfield's promotion dream focuses on the Premiership as Sunderland look to bounce back at the first attempt and this win saw them replace Reading in the crucial top six places.
The Black Cats came into the game unbeaten in six, a run which has taken them to within reach of a remarkable double of promotion and FA Cup final appearance.
But, with Reading beaten only once in their last seven games, a tight game was always on the cards.
The statistics emphatically favoured the visitors, though for all their half-chances Mick McCarthy's side never truly tested Reading's inexperienced keeper Jamie Ashdown in a first half of few real chances.
The 21-year-old, deputising for injured American keeper Marcus Hahnemann, was in the right place to hold Phil Babb's header after the defender had stayed forward following a corner on 41 minutes.
Then, seconds later, the youngster scrambled to his right to hold on to John Oster's skidding low shot.
Other than that, Ashdown was not tested despite a string of Sunderland threats in the first hour.
Kevin Kyle saw two free headers fly just off target after first Steve Brown and then Ivar Ingimarsson had missed defensive headers and Paul Thirlwell lashed over the bar after Ashdown had dropped a corner.
Brown, pressed into emergency action because of a defensive crisis at Reading, was clearly struggling for fitness and was always under pressure from the dangerous Kyle and a lively Byfield.
Reading, for all their possession, took 89 minutes to force a corner and more than an hour to muster a single effort on goal, Andy Hughes heading straight at goalkeeper Mart Poom from a John Salako cross.
Reading's increased goal threat coincided with the arrival of lively young striker Dean Morgan, who replaced the ineffective Shaun Goater midway through the second half.
Morgan, who scored Reading's injury-time winner at Cardiff in midweek, struck fear into a previously unflappable Sunderland defence, with some neat tricks and direct running.
Yet, ironically, Reading's best spell of the game preceded Sunderland's match-winning breakthrough.
Crucially, Brown's fitness was exposed as he failed to track Byfield's run into the penalty area and was beaten in the air as the striker thumped home a header from McCartney's cross.
Two minutes later Sunderland doubled their advantage, though this time the goal was harsh on Reading's hapless defence.
Substitute Smith ran clear despite Reading appeals for offside and, though Ashdown did well to block his shot, the ball cannoned back goalwards off the unsuspecting Ingimarsson.
Brown, on his knees on the goal-line, got a head to the ball to prevent an own goal, but the ball fell kindly for Smith to lash home a crucial second goal.
The two-goal cushion proved crucial as Sunderland were reduced to ten men when Jeff Whitley was sent off seven minutes from time, his second red card within ten days.
Whitley picked up a second booking following a crunching tackle on James Harper, though manager McCarthy was convinced the former Manchester City midfielder had won the ball.
Reading attempted to take advantage of the extra man, Morgan nutmegging a defender and forcing a fine save from the previously under-employed Poom.
The lively Morgan also smacked a shot wide late on, but by then Reading were a beaten side, leaving Steve Coppell's side frustratingly shy of a play-off position.
"I don't know whether we are capable of getting in the top six, but I know have a squad of players prepared to give their all for me every week," Coppell said afterwards.
"But we need our key players to be playing week in and week out to have a chance," Coppell added.
With defenders Adie Williams and Nicky Shorey, top scorer Nicky Forster and goalkeeper Hahnemann all laid low, that is not an option for Coppell right now and McCarthy was aware his side had exposed a gaping hole in the Reading squad.
"We took advantage of their situation," McCarthy said.
"They had a hugely weakened defence. They have Ricky Newman playing at left-back and that is not his position and they had Brown limping at the end of a game he probably should not have played.
"He was a real man out there for them but I was pleased with the way we played and I told the players at half-time not to come away with only a point or even nothing from a game we should win.
"We are on a good run but we are not suddenly claiming to be the best side in the league.
Perhaps we have the best facilities, though Reading might argue with that, but we would not claim to be the best side. But it still annoys me when people fail to give us the credit we deserve."That could all change if Sunderland's impressive run continues, with games in hand on the rest of their play-off rivals and the FA Cup semi-final against fellow first division side Millwall to come in a fortnight's time.
But McCarthy insisted: "All I am thinking about is Gillingham next week. I know people want me to talk about the Millwall game, but if I do that it will come back to haunt me so I'm happy to concentrate on next week."Man of the Match: Kevin Kyle – Led the Black Cats line well with his usual vigour and gave the Royals backline a torrid afternoon.