The St James' Park outfit held strong against Louis van Gaal's men until a calamitous late defensive mix-up led to Ashley Young slotting him in the 89th minute to steal the three points for the visitors.
And Sissoko says Newcastle boss Carver told his players in no uncertain terms that they simply cannot make such mistakes in future.
“I think we played well and had some chances to score but we didn’t and Manchester United scored in the last minute,” the midfielder told reporters. “We’re unhappy at that.
“The manager came in the dressing room and said we can’t make a mistake like we did in the last minute. We played well for 89 minutes and they scored with their last chance. That’s why he was angry."
The defeat very much continued Carver's unimpressive record as Newcastle boss, although that is perhaps a harsh reflection.
The 50-year-old has only won two games as manager of the Tyneside outfit but one of those victories came recently against Aston Villa, while the Magpies did cope well for the majority of their encounter with Manchester United.
Newcastle now have the weekend off as they are not involved in the FA Cup quarter-finals and don't have any Premier League fixtures to contest until next week, when they travel to struggling Everton.
Manchester United, meanwhile, host Arsenal in the Cup on Monday night.