Stajcic: 'The better team won'
An 87th-minute goal from Mana Iwabuchi saw Japan to their win, ending Australia's run at the Women's World Cup in the quarter-finals.
The reigning world champions had threatened throughout in hot conditions in Edmonton.
And Stajcic said Japan were worthy winners.
"Clearly the better team won, even though I thought it evened out a bit after the first 20 minutes," he was quoted as saying by the FIFA website.
"Japan were a lot more composed over the full 90 minutes. We didn’t set out to play any differently, but we just spent a lot of energy in the first 20 minutes chasing the game.
"Most of our players are young, and it is a heartbreaking moment for them, but sometimes you learn from these experiences.
"We don’t want to compete with the best, we want to beat the best, so now it is a case of taking further steps. There is a lot of room for growth moving forward."
Japan needed until late on to secure their win, with Iwabuchi scrambling in from close range after the Matildas failed to clear a corner.
But coach Norio Sasaki said he never doubted his team would find a breakthrough, while he also paid tribute to the Matildas.
"Even if we didn’t get a goal within 90 minutes, I felt we would get it inside 120 minutes. The game plan was executed very well," he said.
"We recognise the growth of Australia in this World Cup and my team will take confidence from this and we can build with future success.
"Also the solutions we came up for this match worked very well, and this also gives us confidence.
"We will fight hard in the semi-final being mindful of the people supporting us back in Japan."