Nicholas, who starred for Aberdeen between 1987-90, believes that even if the struggling club scrape into the top six, not enough progress has been made and it is time for a change of manager.
Nicholas, who played for the Dons from 1987-90, told the Scottish Daily Express: "I saw Craig Brown quoted as saying his team could be up challenging for second spot. At the moment, they look like they will be closer to second bottom.
"Craig’s contract runs out at the end of the season and I just don’t see any way, even with a top six finish, it can be renewed. All the other teams look like they have a momentum and it seems the tide has turned on Craig."
Nicholas, who is a regular pundit on Sky Sports, says he has noticed a change in Brown's behaviour and perhaps he knows his time is up - and with crowds disappearing, it should come sooner rather than later.
"[Brown's] response after the Ross County game, a match they deserved to lose, was that he had no excuses," said Nicholas. "He normally comes out with some sort of statistic, but there was nothing.
"Come the summer it should be time up. I don’t think a new contract will now be in the thinking of the Aberdeen board.
"The Aberdeen fans have lost interest, you can see that with the way their crowds are dwindling.
"I watched a bit of the Ross County game on Tuesday night and I thought to myself no wonder the fans don’t want to go."