Sunderland's derby day celebrations came to an abrupt end as a Carlos Cuellar own-goal and two red cards saw them defeated 1-0 by Hull at the KC Stadium.
Having beaten rivals Newcastle last weekend, defeat here will have been a huge comedown for manager Gus Poyet - who would have been fuming about an inexplicable lack of discipline that saw Lee Cattermole and Andrea Dossena sent off within moments of each other at the end of the first half.
By then Hull were already in front, Cuellar turning a Liam Rosenior cross into his own goal under pressure from Yannick Sagbo.
But the fact that the Tigers could not add to their lead in 45 minutes of 11 against nine will leave Black Cats fans wondering what might have been.
Adam Johnson even had a glorious chance to level the scores in the 78th minute, Steve Harper making the crucial save, while Jake Livermore hit the post at the other end.
But that will surely matter little to Hull boss Steve Bruce, who was facing the Wearsiders for the first time since being sacked by them amid a torrent of abuse from the fans.
Bruce was not the only one to get one over his former club, with Paul McShane, Ahmed Elmohamady and David Meyler - a last-minute replacement for the injured Sone Aluko in Hull's starting XI - all former Black Cats.
After a cagey start Hull created the first real chance in the 17th minute, Tom Huddlestone's free-kick finding Curtis Davies whose flicked header narrowly evaded both Livermore and McShane.
In the 25th minutes the hosts were in front thanks to the own-goal.
John O'Shea was partly responsible, needlessly heading out of play to give Hull a throw-in deep in Sunderland territory.
Rosenior took it and when the ball made its way back to him sent in a fizzing near-post cross for Sagbo.
He flung a leg at it but it was his marker, Cuellar, who unwittingly headed past Keiren Westwood from a tight angle.
Westwood's afternoon was cut short by injury when McShane clattered him, unintentionally, while looking to get on the end of another Davies header.
The Ireland keeper attempted to play on but was visibly groggy and was forced to make way for Vito Mannone, a former Hull loanee.
Buoyed by the goal Hull kept possession for the best part of five minutes, with the home fans greeting every touch with a traditional 'Ole'.
Whether or not that contributed to the Black Cats' frustration is hard to know, but they soon betrayed a recklessness that left them two men down at the break.
Cattermole was the first to go, lunging in with studs up on Elmohamady after he had exchanged passes with the busy Meyler.
Cattermole is well used to seeing red and appeared unsurprised to be on his way.
With five minutes added time for the Westwood injury, Sunderland would have been hoping for no further drama before the break.
But Dossena ensured that would not be the case when he stamped on Meyler over the top of the ball.
Andre Marriner produced his red card again and the visitors went in reeling.
Poyet made two changes at the break, Johnson and Wes Brom replacing Jozy Altidore and Fabio Borini.
Regardless, Hull dominated possession as expected.
A couple of hopeful efforts sailed over before Livermore played in George Boyd, who bundled past Cuellar before shooting just wide across goal.
With Steven Fletcher frequently the only red and white shirt in the Hull half, Sunderland managed to reach the hour-mark without conceding a second.
Livermore went closer than most with a deflected effort that Mannone reacted well to save but O'Shea and Cuellar were largely doing well against the odds.
Sunderland gave Hull a couple of reminders that their lead was still a slender one - Johnson shooting wide of the upright after a sloppy clearance from Maynor Figueroa and Seb Larsson putting a dangerous free-kick into the side netting.
Bruce made a pair of attacking changes as looked to seal the points, Robert Koren and Nick Proschwitz replacing Meyler and Rosenior, with Elmohamady slotting in at right-back.
But Sunderland should have drawn level with 12 minutes left when Johnson got on the end of a long ball and was denied by Harper from a glorious one-on-one position.
It was a crucial intervention by the former Newcastle man.
Within seconds the ball was at the other end of the pitch, Livermore rattling the post from 20 yards and that was the closest either side came to adding to the score.