The Australian felt they did not give a good enough account of themselves on Tuesday night.
Spurs were beaten 2-0 at home by Manchester City, which means they will finish fifth in the league this term.
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"The foundations are really fragile," the Australian said to reporters of the club post-game.
"The last 48 hours have shown me that.
"It's inside the club, outside the club. Outside, inside, everywhere. It's been an interesting exercise. It's just my observations, mate."
On the atmosphere being flat, as many fans did not want the team to win to help Arsenal's Premier League title bid, he added: "Of course it does. It is what it is. I can't dictate what people do.
"They're allowed to express themselves any way they want. But yeah, when we've got late winners in games it's because the crowd's helped us."