Son and Maddison were forced off late on during last weekend’s 2-2 draw at Arsenal after not being “100 per cent” for the derby, according to the Spurs boss.
The influential duo both trained on Friday and Postecoglou remains confident they will feature against Jurgen Klopp’s team, but Brennan Johnson will be absent.
He said: “From last week, Brennan will miss out. It’s nothing too serious but he won’t be right for this week.
“Madders and Sonny trained today, just finished the session and seemed to get through it not too bad.
“We’ll just have to see how they pull up as it’s fair to say they were a bit sore after last week and had a bit of an interrupted week training, so just a matter of seeing how they pull up.”
Maddison and Son combined twice at the Emirates to earn Tottenham a 2-2 draw and maintain their unbeaten start to life under Postecoglou in the Premier League.
Summer recruit Maddison suggested post-match the club were beginning to shed their ‘Spursy’ tag after they showed plenty of grit to peg back Arsenal on two occasions last Sunday.
“I haven’t heard exactly what Madders said but he is obviously new to the club and is going on what he is feeling at the moment,” Postecoglou reflected.
“It is fair to say the lads have shown a fair bit of resilience this year and we’ve had to adjust to the nature of the way the games have gone. We have had a lot of things in the context of a football game that haven’t gone our way.
“Sometimes these things can become a little bit overblown because opposition supporters are obviously looking for any kind of sore point that a football club may have.
“This club has been up at the top of the table for quite a while now and got close to having the ultimate success in the Champions League, so it is far from being a club that has fallen on bad times for a long time.
“Obviously there is a crucial bit missing there and every group of players, myself included, have the opportunity to change that.”
Liverpool boss Klopp had been full of praise for Postecoglou during his press conference earlier on Friday and the Australian returned the favour.
Postecoglou added: “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.
“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.
“Because 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.”