Both Liverpool and Spurs are two of four unbeaten teams left in the Premier League this season, but Jurgen Klopp's side are on the longest unbeaten run among clubs in Europe's top leagues, last losing in April in the 2022/23 campaign.
Liverpool were eighth at that time last season but ultimately finished fifth and although they failed to qualify for the Champions League, Postecoglou said the Anfield side are on the rise again.
"They've been a very good football team for a while now. Obviously, they fell off the pace last year a little, but the elements of who they are as a football team have always been there. It's a great test for us," Postecoglou told reporters.
"They probably bring something different from any other team in the league in the way they play and the manner they go about things.
"It'll be a really good test for us to try to impose our football on a team that's fairly unique in the way they play the game."
Spurs have also been a team on the rise since Postecoglou took charge, with a wave of optimism sweeping across the white half of North London after the club had their best start to a league season in 57 years.
While Postecoglou has only begun to leave his mark, the Australian praised Klopp for what the German had brought to not just Liverpool but the entire league, marvelling at their high-tempo playing style offensively and defensively.
"Jurgen is an outstanding manager, he's one of the managers I think it's fair to say who has made an impact on the competition, not just his club," Postecoglou said.
"When he came in, with the way Liverpool went about things, he challenged quite a few of the conventions about the Premier League and introduced a new style of play that others have followed.
"It's a great test for where we are at the moment in terms of our development."
Postecoglou said forward Brennan Johnson will miss out on Saturday with injury while James Maddison and Son Heung-min will be assessed.
"Madders and Sonny trained today, just finished the session and seemed to get through it not too bad," he said.
"We'll just have to see how they pull up as it's fair to say they were a bit sore after last week."
