Brendan Rodgers faced dissent from the stands and apparent disquiet from within his squad following Saturday’s goalless home draw with St Johnstone.
Celtic followed their Viaplay Cup exit at Kilmarnock with another setback as they saw their early-season cinch Premiership advantage over Rangers cut to one point before travelling to Ibrox next Sunday.
Celtic were booed off the park after failing to break down a team who had lost their last four matches.
There was further acrimony as Rodgers joined his players as they walked round the stadium to show their appreciation to the fans who had stayed behind.
Many of those in the standing section, which had expressed opposition to Rodgers’ reappointment in June, reacted angrily when the group reached them.
There was another issue for Rodgers to ponder on Sunday when Sead Haksabanovic appeared to express dissatisfaction with his situation on the fringes of the team.
Writing on his verified Instagram account, Haksabanovic posted a photo of himself in a Celtic strip and said: “If they don’t see your value maybe you’re not at the right place.”
The Montenegro international has only started 13 games since joining Celtic 12 months ago, four since the World Cup, and has made two substitute appearances under Rodgers.
The comment quickly drew criticism from former Celtic striker Chris Sutton, who wrote on Twitter: “Haksabanovic may have a point but he’s out of order making his point in public.
“Just go and knock on the managers door and tell him if you’re unhappy… and playing well also helps!”
Haksabanovic came close to breaking the deadlock against Saints with a long-range strike that was turned round the post by Dimitar Mitov.
The Bulgarian goalkeeper made a hat-trick of excellent stops from Matt O’Riley but was otherwise untroubled by Celtic, who needed Joe Hart to be on top form to deny Dara Costelloe and Stevie May in the second half.
Celtic failed to score in consecutive domestic games for the first time in five years, the previous time coming after they had clinched their second title under Rodgers.
Some players appear to have lost their edge since the departure of Ange Postecoglou and Rodgers could not explain the reasons for their flat display in the immediate aftermath of Saturday’s game.
Rodgers said: “We obviously had a couple of good chances, the keeper made some really good saves and we got into some good areas, but we lacked craft and that extra wee bit of imagination when we got in there.
“I’m not sure (why). I think it’s something I need to go away and analyse in the game. We arrived into some good positions but whether it was the finesse on the pass, or giving it away, or just couldn’t quite beat our man.”
Despite the setback, O’Riley feels they are getting greater cohesion.
The midfielder, who is playing a deeper role than he normally fulfilled under Postecoglou, said: “I think structurally we were better in terms of our understanding on the pitch.
“We could have been a lot cleaner with our passes but in terms of understanding the system, today was the most comfortable I’ve felt within it. I think that showed with the chances we did create.”
St Johnstone manager Steven MacLean hopes the point will kick-start their campaign after a difficult start to his first full season in the job which saw his side lose five of their first six matches and suffer a 4-0 home defeat by Stirling.
“This was the first week that we had a proper squad,” said MacLean, who handed out three debuts. “We had 12 players fit for pre-season and four of them were young players who’d never played for the club before.
“I had 10 players injured at Ross County, and had to play a left centre-half at left-back and a central midfielder at right-wing.
“The things that have happened in the off season, you couldn’t write it. You go on all these courses to learn about coaching and managing but nothing like that gets brought up.
“There have been some tough days but you come through it and you are better for it. Hopefully my team can kick on now.”