Spurs offered little fight at Anfield as Liverpool were confirmed Premier League champions with this result.
Postecoglou said afterwards: "Credit to Liverpool, worthy champions and they have been the outstanding team all year, consistent and again today obviously. I thought we started the game well and sort of made things difficult for them.
"Even apart from the goal, I thought just in general we had decent territory but once they got in front with the atmosphere inside the stadium fair to say it was going to be difficult for us to claw them back and that's how it proved.
"It's not easy, it's not easy on the players because if you sort of look at Liverpool's line up you can almost pick it on a weekly basis. I had made a lot of changes but I just felt it was necessary. A lot of our players have missed a lot of this season with injuries and it wasn't just about bringing them back but managing their minutes because obviously we want them ready.
"Guys like Micky (van de Ven) and (Cristian) Romero today could have played but they've missed so much of the season that we've just got to be really careful about when we use them. Guys like Pedro (Porro) and (Rodrigo) Bentancur have played a lot this year. It has been a juggling act for sure and that hasn't helped the team, hasn't helped the players and when you're facing the best you pay that price."
"There won't be a hangover for semifinal"
Asked if the result was a concern ahead of their Europa League semifinal against Bodo/Glimt on Thursday, Postecoglou was confident in his players.
He added: "No I don't think so, I think they are well aware of it. Like I said, we had some key players missing today who I think will come in and sort of make sure there isn't any hangover from today. Look, we knew the challenge today was going to be a big one.
"We had a really young midfield with Lucas (Bergvall) and Archie (Gray) and you're asking a massive task of them. Change three of the back four, all of these kind of things logically tell you it's going to be a tough day, but when you're facing the best team, and on such a massive occasion, it was always going to be a huge ask for us and it proved too much."