Kean booted out the Senegal international in September following a string of bust-ups.
Rovers crashed to their eighth defeat of the season at Stoke on Saturday. And Diouf, who is now at Doncaster, said: "Everyone knows Blackburn haven't got the team to stay up.
"Any other manager with the team in that position would have been sacked.
"The owners will see their side go down unless they make a change. I fear for the club. No one there deserves this."