The 41-year-old has seen his team pick up back-to-back draws in the Premier League after a shock win over Manchester City, but has acknowledged that Tottenham will pose a different threat.
Spurs sold prolific winger Gareth Bale to Real Madrid for a world-record fee during the transfer window, but have made a solid start to the new season thanks in part to new signings Roberto Soldado, Erik Lamela and Christian Eriksen.
And Mackay has hailed Andre Villas-Boas' new-look team ahead of his side attempting to deny them points on Sunday.
"The players they brought in everyone in football knew they were top talents," he told the Daily Mail.
"We knew they were on the market but would cost a lot of money. Again, though, because of the extraordinary amount they brought in from the Bale deal meant they could do it.
"The squad looks like a Champions League squad. They are in that bracket (with Manchester United, Manchester City and Chelsea).
"They have a squad full of quality. I have no doubt that we will be facing a team up for it and packed full of quality.
"They have bought very well. They had a real match winner in Bale. He has that quality. He left a huge hole but they filled it well. The extraordinary size of that fee let them bring in seven or eight quality players. It has changed Tottenham."
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