Neil Lennon's Celtic woes continued as his side were held to a 1-1 home draw by St Johnstone to leave them 13 points adrift of Scottish Premiership leaders Rangers.
Chris Kane put St Johnstone ahead in the 79th minute and the visitors held out for the point after substitute Mohamed Elyounoussi headed an equaliser four minutes later.
Lennon clung on to his job following angry protests outside Parkhead after last weekend's Betfred Cup defeat by Ross County.
But the Celtic power-brokers will come under increased pressure to make a change with their hopes of a 10th consecutive title slipping further away following Rangers' 4-0 victory over County earlier on Sunday.
They have two games in hand but any further slips would put the title race out of their hands.
Celtic lacked width and penetration in an even first half and they could not find a clinical touch despite pushing their visitors back for much of the second period.
In normal circumstances Celtic would welcome the chance to play St Johnstone, having scored the previous 34 goals in the fixture. However, Callum Davidson's side were the form team coming into the game.
Since Celtic won 2-0 in Perth two months ago, they have recorded just two victories in 12 matches, conceding 28 goals. They had suffered three successive defeats and four on the trot at home before the visit of Saints, who stretched their unbeaten run to 11 games.
Saints had the first chance when David Wotherspoon's free-kick eventually fell kindly for Stevie May but the striker's effort was headed off the line by Nir Bitton.
The hosts soon had a good opportunity from their own free-kick but Tom Rogic headed wide.
The only other real opportunity of the half came after Callum McGregor played Odsonne Edouard through but the Frenchman's effort hit the legs of Zander Clark.
Saints lost Michael O'Halloran after he failed to run off the effects of a Scott Brown foul but, with Kane on in his place, they continued to hold their own.
Lennon had lined up with a three-man central defence with wing-backs Jeremie Frimpong and Diego Laxalt charged with providing width, but they were struggling to get down the outside of an organised visiting defence.
Greg Taylor replaced Laxalt at half-time and May blazed over from a half-chance 30 seconds after the restart.
Celtic soon came close following a corner, but Clark made another stop from Edouard after the striker flicked on Christopher Jullien's header and Brown could not convert the bouncing ball.
Brown's 600th Celtic appearance lasted 59 minutes before he was replaced by Leigh Griffiths. The midfielder handed the armband to McGregor, who was playing his 300th game for the club.
Edouard hit a free-kick into the wall before Jullien headed wide from a Griffiths corner. Clark got down well to push substitute David Turnbull's long-range drive wide but the visitors soon took the lead when Kane converted May's low cross from the left at the far post.
Clark made a save from Edouard before Elyounoussi levelled with a header from Ryan Christie's cross, which looped high over Clark and landed just under the bar.
Turnbull and Elyounoussi headed wide as Celtic pushed for a winner but they came up short again.
