John Barnes insists Eddie Howe and Celtic must set out "the kind of relationship they want".
The former Parkhead boss reckons expectation over what the incoming manager's remit will be need to be made clear.
He particularly points to whether Howe will want to spend big in the transfer market or work to squeeze more from Celtic's current crop.
Either way, however, he warned the club should not immediately expect to overthrow Premiership champions Rangers.
He told BettingOdds.com: “Like the right players looking for the right type of football to suit them rather than the club, I think Celtic and Eddie have to decide the kind of relationship they want.
“Is Eddie going to say, 'I want to go and work at Celtic with what I have so I can make them better but I will need to be given time, it’s not going to work all of a sudden'? Or is he going to be like a big name European manager who’s going to expect to spend millions and get better players in?
“Because it’s Celtic and they have to challenge Rangers, they could go for a superstar manager and spend loads of money to get better players.
"That’s why you have to look at the dynamic of the club’s ambitions as well as the manager’s ambitions.
“I think working with what he has, Eddie will do a good job, but he’s not all of a sudden going to be better than Rangers.
“Rangers have got better players than Celtic and they’re in a better place, so the expectations of beating Rangers are maybe unrealistic.”
