Two late goals by League Two Newport County sent the Championship outfit crashing out at the third-round stage on an afternoon when Christiansen made nine changes to his starting XI.
In contrast, Exiles chief Michael Flynn kept the same line-up that had beaten Exeter City on New Year’s Day and was rewarded with a performance that was superior to that of Leeds in every single aspect.
United’s exit had similar hallmarks to last season, when then head coach Garry Monk infuriated fans by making 10 changes as the Yorkshire side were humbled by non-League Sutton United.
“It was very bad,” said a chastened-looking Christiansen in the wake of his side’s 2-1 loss in south Wales. “The result was the worst and we didn’t give everything that we have during the game.
“We were not intense enough and, unfortunately, we are out. I take the blame. Always the manager takes the blame. I will do that also.”
United lacked cohesion throughout, something that critics will suggest can be put down to the multitude of changes made by Christiansen.
Asked if he had disrespected the FA Cup, the Leeds head coach replied: “At our press conference (last Friday), I said I didn’t want anyone to disrespect any teams.
“Newport deserve respect. Over 90 minutes you have to prove you are better. In this match we didn’t do it.
“But if you look, every player we had in the first XI against Newport is a player from the first team. These are players who have possibilities in the first XI.
“For this we expect more and it should be enough to pass to the next round.
“The players know what it means. If I know what the FA Cup means and I come from Denmark, or am half-Spanish, then if they don’t know it they are not in the right situation.”
United’s misery was compounded by Samuel Saiz being dismissed for spitting at Robbie Willmott in the immediate aftermath of Shawn McCoulsky’s dramatic 90th-minute winner.
The Spaniard, by some distance the club’s most impressive performer this season, is facing a lengthy ban to exaggerate the misery of what was already a desperate day for Leeds, who earlier in the season had beaten Newport 5-1 in the Carabao Cup.
Premier League Burnley were also knocked out at the third-round stage by the Yorkshire side and Christiansen pointed to that shoot-out triumph at Turf Moor as proof that making wholesale changes does not necessarily weaken a side.
He added: “Against Burnley I also made 10 changes and they made it with a perfect performance. Against Leicester we made nine or 10 and did very well, so why not this time? What is the difference?
“I don’t know if it is attitude. We just needed to put more into the game and understand where the danger came from and how to combat that.”
Following on from the exit to Sutton in last year’s fourth round, yesterday’s defeat brought stinging criticism from the travelling supporters who helped Newport to comfortably their largest crowd of the season, 6,887 being inside Rodney Parade.
“I am sorry for them because it is a long journey and they spend their money,” added Christiansen. “I would also be disappointed to make this trip and not take a good result.
“But this is football, these things happen and this is what makes the FA Cup special. You know that this can happen, but you never want it to happen to you.
“Now we need to focus on another competition.”
As for Saiz’s red card, Christiansen added: “I didn’t see it. If it is right why he got the red card it is a problem. But I believe that he didn’t do it.”
United’s defeat means there will be just five Yorkshire clubs in tonight’s fourth-round draw.
Middlesbrough, Hull City, Sheffield United and Huddersfield Town are all through after victories on Saturday while Sheffield Wednesday must negotiate next week’s replay at home to Carlisle United to take their place in the next round.