William Gallas has warned Ange Postecoglou it will be a difficult task to finish in the Champions League places this season.
The former Spurs defender doesn't expect an immediate rise to the top four under Postecoglou this season.
And he suggested Spurs are a bigger club than Celtic as he cited the "pressure" to ensure the club makes a good start to the league campaign.
And of Postecoglou's major job in North London, Gallas set the first challenge to fix the leaky defence.
Speaking to Gambling Zone, Gallas said: "My first question for the new manager is 'Did you see the problems with Tottenham’s defence last season?'.
"We know that he has a pedigree of playing attacking football and likes his teams to play in a certain way, but Tottenham have problems at the back. They concede so many goals – sometimes stupid goals – so that will be the first problem that Tottenham need to solve.
"You can have the best striker in the league, but if you don’t have top class defenders, you will always concede goals and lose matches.
"This is the biggest club that Postecoglou has ever managed, so there will be a lot of pressure on his shoulders and the fans will expect him to get off to a good start straight away. I’ve heard that he has a lot of good people around him that are helping him.
"I’m not sure what will happen at Tottenham this season. I can’t see them finishing in the Champions League places."
Gallas' "biggest club" remark comes after Robbie Savage stated Postecoglou had downgraded from Celtic.
The pundit said: “I think [joining Tottenham] is a brilliant step for Ange Postecoglou – even though he’s dropped down in club size. He was brilliant with what he did at Celtic, particularly with the brand of football – I keep a close eye on the Scottish Premiership, and you have to win the league if you’re Celtic or Rangers, which he did convincingly by winning the treble.
“But Spurs haven’t got that star [for winning the European Cup] on their shirt like Celtic do, nor do they have Champions League football like Celtic, so is it a gamble for him? He needs time at that football club, it’s as simple as that – look what happened with Jose Mourinho.
“The club are going with proven winners in recent years, and Postecoglou was winning at Celtic, so will he regret it? He was adored there, had Champions League football, and would probably go and win the Scottish Premier League again, so I think he’s taken a step down.”
