Ross County piled more pressure on Neil Lennon by knocking Celtic out of the Betfred Cup.
Ross Stewart's 39th-minute penalty and Alex Iacovitti's late header earned County a 2-0 second-round win to ensure Celtic's run of domestic success will finish this season.
Celtic can make it 12 consecutive trophies if they beat Hearts next month in last season's delayed Scottish Cup final but their 35-match winning run in domestic cups ended with an uninspiring display at Celtic Park.
It was a first cup defeat since Ronny Deila's side lost to Mark Warburton's Rangers in the semi-final of the Scottish Cup in April 2016.
Lennon declared he had the full backing of majority shareholder Dermot Desmond and chief executive Peter Lawwell after Celtic crashed out of their second European competition of the season on Thursday.
But Celtic have now won just twice in 10 matches and, although they missed several good chances, they looked a team lacking in ideas and confidence.
The Green Brigade, a prominent fans' group, had called for Lennon's departure before the Europa League exit was confirmed and the demand for change will intensify after a poor display.
Celtic are 11 points behind Scottish Premiership leaders Rangers, albeit with two games in hand, and the manner of their defeat will intensify feelings among a growing band of supporters that they will not recover without change.
County have not won in seven Scottish Premiership games and manager Stuart Kettlewell had declared last weekend's 3-1 defeat against 10-man Kilmarnock one of the worst results in his 12 years with the club.
Lennon changed his formation to a 3-5-2 following Celtic's second 4-1 defeat by Sparta Prague in three weeks. Defender Nir Bitton and striker Albian Ajeti came in for midfield pair Callum McGregor and Mohamed Elyounoussi while Vasilis Barkas replaced Scott Bain in goal.
There was little in the game before the opener and Celtic lacked the width to get in behind County. Ryan Christie had a shot comfortably saved after a counter-attack and Tom Rogic shot into the side-netting after a corner either side of Celtic's best chance for an opener.
That came after Christie had looked to have weaved his way through the County defence before being tripped on the edge of the box by Callum Morris, who avoided a card of any colour. Ross Laidlaw pushed away Odsonne Edouard's free-kick.
County, who lost Charlie Lakin to injury early on, had threatened from two long-range efforts from Harry Paton before taking the lead.
Josh Reid streaked away down the left and Christopher Jullien brought Stewart down as he made a desperate attempt to stop the striker getting to the wing-back's low near-post cross. Stewart sent Barkas the wrong way.
Ajeti had a glorious chance to equalise inside two minutes after a Rogic flick played him clean through, but the Swiss striker hit the inside of the post and the ball rebounded to safety.
Diego Laxalt and Christie were off target from half-chances and Kristoffer Ajer had an effort saved following a set-piece but Celtic struggled to break down a packed County rearguard and Lennon made a double switch midway through the second half.
McGregor and Elyounoussi came on for Ajeti and Bitton as Celtic reverted to a back four.
They immediately created an excellent chance but Elyounoussi headed wide from eight yards after Rogic's cross found him unmarked.
Edouard hooked a volley over before Lennon brought on Shane Duffy for right-back Hatem Abd Elhamed.
But County doubled their lead in the 84th minute when Iacovitti nodded home after an Iain Vigurs corner had been flicked on to the far post.
