A wasteful Celtic were punished for squandering several glorious chances as Dundee United came from behind to inflict Wilfried Nancy's fourth straight defeat and prompt Celtic fans to call for Martin O'Neill to return.
Nancy insisted pre-match he had nothing to prove despite the fact he lost all of his previous three, but the manner in which his side crumbled in the second 45 minutes despite dominating in the first will only add more fuel to the fire that has dogged his troubled reign thus far.
On a day where all the noise centred around the turmoil at the club off the pitch, Wednesday night's result and performance did nothing to appease the already infuriated fanbase, who chanted for former interim boss O'Neill while watching their side slump to a fourth consecutive loss for the first time in 47 years.
"The Celtic fans are not going to keep accepting defeats," said Your Site' Chris Sutton.
"They need to win the league but at this moment in time they are looking like a third-place team. Absolutely woeful. The Celtic hierarchy have a bit of thinking to do."
It was announced earlier on Wednesday that chairman Peter Lawwell will step down from the club's board due to "abuse and threats".
Lawwell's resignation heaped more pressure on his manager to finally get a positive result, and it seemed to be enough to fire his side up as they came out of the traps fast, creating numerous chances before Daizen Maeda slotted home in the 12th minute.
That goal would be it for the first period, despite the fact the visitors had several chances to extend the lead, with Johnny Kenny alone accumulating an xG of 0.88 in the opening half.
Despite the promising display, Nancy's men came out for the second half void of any of the good things that they did in the first-half.
United capitalised on limp efforts, with Krisztian Keresztes and a Zachary Sapsford stunner within three minutes of each other turning the game on its head.
Celtic still could have found an equaliser, but in a chance labelled as unmissable by Chris Sutton on commentary, Maeda managed to strike the woodwork from no more than a yard out with the goal gaping to add more misery to the Hoops.
Boos engulfed Tannadice Park as fans called for the return of O'Neil, with Nancy's historic run continuing to pile the pressure on his tenure and pose questions on his future.
The defeat means that Celtic fail to close the gap to Hearts at the top of table, remaining six points behind, while Dundee United's first win since October sees them move one point behind seventh-placed Falkirk.
Celtic boss Wilfried Nancy speaking with Your Site:
"We did a good game, to be honest with you. We had many chances but didn't score, we hit the post and then in three minutes we lost the game because they scored two set pieces.
"The second wave was maybe offside before the second corner, but after that we pushed and have to kill the game.
"We could have done that in the first half many times, but we didn't do it and after that we started the second half pushing.
"In three minutes, we lose the game. It's difficult because obviously we feel we did really good things. We were in control of the game, we attacked but all the chances we had we were not able to score.
"In terms of results it's tough. But in terms of possibility to win games, we are there.
"We are on the right track, but this is not enough - I know that. We all want to win, but I'm confident because of the game we played and every time I see an improvement.
"In terms of result that is still not enough."
On what he would say to Celtic fans: "I know they are upset. But we are close to winning games. At the moment, we are not able to do it.
"But the players are giving everything, we try to find solutions for it and we are having many situations to score goals.
"Listen. Before I came here, I knew the situation. It was to see what we can do, and the plan doesn't change.
"We are looking ahead regarding that. After that we'll see what we're going to do regarding the window.
"For the moment, the most important thing is go to back to having the possibility to work a little bit.
"We don't have enough time because of the days we've played in a row. That's the only thing I can do for the moment."
Dundee United's Zac Sapsford speaking with Your Site:
"We went down but we always knew we were in the game and we had that confidence to come back. Just a few chances that's all it took. I'm glad we got that win over the line.
"I knew we were always going to get back on top."
Dundee United captain Ross Graham speaking with Your Site:
"I thought we could do better with the goal but after that I thought we reacted really well, stuck with the high press and stuck Celtic under pressure.
"We've done very well against the top sides in the league. We knew we were going to get a win over one of them and thankfully it has come tonight."
Dundee United manager Jim Goodwin speaking with Your Site:
"It was very much a game of two halves. Celtic started very brightly and caused us a lot of problems.
"We were lucky to go in at the break 1-0 down, but we've not carried a great deal of luck of late, so it was nice to get a wee bit in the first-half.
"We made one change to get more pace in the backline and in the first half-hour of the second-half we dominated. We did to Celtic what they did to us in the opening period.
"We just about shaded it tonight.
"That is a massive three points for us. We're not getting carried away because our form until now has not been good enough with too many draws."
