The center half is nearing the century mark for Spurs, as playing at the weekend will make it 100 games in North London.
Asked about what he has made of Romero in the year they have been working together, Postecoglou was effusive in his praise.
He told reporters: “Outstanding. Obviously with all these kind of things you have the image of a player from afar and before I got here I thought he was going to be really important to me because he's such a fantastic centre-back for club and country.
“But being here, watching him, the way he trains and the way he plays, unbelievably string mindset. An absolute winner in every thing he does. He was really important last year and he's going to be really important moving forward.
“He is one of the players within this group who has achieved things from a team perspective and those kind of things are transferable. He has won the World Cup, he has won the Copa America, so he's part of a successful team and I think he's a really strong influence in the group.
“It's great he plays his 100th game tomorrow. I know he'll perform at the level he normally does, he's really consistent, but hopefully we'll make it a special day for him.”