Alan Stubbs fears Neil Lennon has lost his Celtic "alibi" with the impending departure of Peter Lawwell.
The club chief-executive announced last week he is set to retire this summer after 17 years at the helm.
Lawwell has backed Lennon in the face of fierce calls for his sacking this season and Stubbs has a theory as to why the board haven't dismissed the manager.
He suspects Lawwell will be reluctant to end his professional relationship with Lennon on a sour note and has therefore opted not to sack him.
But Stubbs, a former Celtic centre-back, reckons the CEO's exit will leave Lennon "even more vulnerable".
He told Go Radio : "From now until the end of the season, no matter what results Celtic get, it's about looking at the bigger picture.
"I respect Neil Lennon 100 per cent, he's been remarkable in terms of his tenure and what he's achieved.
"But I just don't know, with his biggest alibi in Peter Lawwell going, that leaves him even more vulnerable.
"With Peter going and it's all come out, I think the last thing Peter wanted to do, because of the relationship he's had with Neil, is sack him and end it on a really sour note."
However, Stubbs is adamant the blame for a disastrous campaign cannot be laid solely at Lennon's door.
He insists players failing to take responsibility during matches has been a major factor.
Stubbs added: "That's been a big problem for Celtic and that's not necessarily Neil's fault.
"Neil will carry the can for everything that goes wrong at Celtic and, as a manager, you have to accept that.
"But this is where his staff have questions over them. If they can see that and have not said anything or, even worse, not put it right then that doesn't say a lot about them either."
