Manager Neil Lennon's conduct is a "problem" for Celtic, says former player and assistant Murdo MacLeod.
Lennon rounded on ex-players, the media and Scottish government on Monday for "a barrage of hypocrisy" over the club's controversial trip to Dubai.
Celtic have had two players test positive for Covid-19 following their return from Dubai, while Lennon and 13 squad members had to self-isolate.
"He's obviously been angry since he arrived back home," said MacLeod.
- Second Celtic player tests positive
- What now for Celtic & Lennon?
- Livingston 'imposed style' on Celtic
"He wants to have a go at people. For me, that's not going to help Celtic. When your chief executive puts a statement out and apologises to the supporters [for the Dubai trip] and then for Neil to come back and have a real go like this, I think that's a problem for Celtic now.
"There's so many people listening to Neil and saying, 'This is not the way the Celtic manager should be acting.'"
In Lennon's absence Celtic drew with Hibernian and Livingston, leaving them 21 points behind Scottish Premiership leaders, albeit with three games in hand, in pursuit of an historic 10th successive title.
MacLeod believes Celtic's form this season makes Lennon's position increasingly untenable.
"I think not so much his rant, but what is happening on the pitch," he told BBC Radio Scotland when asked if the Northern Irishman should leave his position.
"But the hardest thing for Celtic is getting a new manager who is going to bring success and win every week and avoid the kind of run Celtic have been on since the end of October. "