The interim manager was left to chew over another abject home performance by last season's champions as the Black Cats took advantage to seal a potentially priceless win
The Mackems' travelling fanbase rejoiced in what could prove a crucial victory in their bid to stay in the Premier League while Giggs and United will have to reflect on a seventh home defeat this season - the first time they have managed that ignominious feat since the 1973/1974 season, when they were relegated.
Sebastian Larsson ultimately consigned the hosts to defeat, and Giggs believes his charges were lacking on two fronts in their efforts to break through a resilient Sunderland rearguard.
|MAN UNITED LATEST
|7/1||Hull are 7/1 with bet365 to beat Manchester United at Old Trafford|
"[It was] probably a lack of quality in the final third," he told reporters. "The first half we got some decent crosses in from [Ashley] Young but we just didn't get enough people in the box really.
"The second half we had all the possession but just couldn't find that key pass or that bit of quality which would have got us back in the game.
"I'm sure if we had scored, we would have gone on to score a few more but it was a lack of quality and a lack of concentration in the final third."
Giggs was at a loss, however, to explain just why United have found few home comforts from Old Trafford this season.
When quizzed on United's home form, Giggs said: "I don't know, because I still believe there's quality in the dressing room and we showed that last week but we didn't this week.
"Whether that be a lack of confidence or a lack of concentration, I honestly don't know.
"We have shown it away from home, good away form, but Old Trafford seems to have been the problem this year.
"In past seasons, even today, there would be wave after wave of shots and you could always sense a goal was coming but this season it doesn't seem to have happened."
Giggs also added that United would continue to "monitor" Wayne Rooney's fitness, with the striker ruled out due to a combination of a groin injury and illness.
Sunderland manager Gus Poyet, meanwhile, was delighted that his side were able to inch closer to survival after a "unique" run of form, but also urged caution despite the seemingly doomed Norwich City's uncompromising fixture list.
"I'm feeling great," he said. "Our idea was always to win four games. We won three and drew one but we need to concentrate on what we do.
"We are in a position where we have two games at home, we win one and we are over the line but, as you know, what we have done in the last four games is unique and special."