Janko was supposed to be in action for his nation against Brazil in an international friendly, but he opted to skip the fixture and return to Sydney as the South Americans ran out 2-1 winners in Vienna.
The 31-year-old club marquee is now back in Australia preparing for Sydney's A-League clash with Melbourne City at AAMI Park on Saturday.
If Janko - who helped Austria move to the top of Euro 2016 qualifying in Group G with a 1-0 win over Russia last week - stayed abroad he would not have returned to Australia until Friday, hampering his chances of facing City.
"It was a tough decision to make because it's a once in a lifetime opportunity to play against Brazil, but I chose not to play this game to be ready for the game against Melbourne on the weekend," Janko told the Daily Telegraph on Wednesday.
"I wanted to be fresh and in good shape and if I had played Brazil I would have played with huge jet lag and the risk of getting injured is very high.
"I didn't want to take that risk, so I decided to come back earlier and deny that big game because I want to please Sydney FC as well and I respect that I have a contract here."
The selfless gesture was appreciated by Sydney, who have enjoyed a strong start to the season and are unbeaten through the first six rounds.
Janko, who scored a stunning debut goal in the Hyundai A-League against Brisbane in round three, has been an important figure in the side's form.
"I'm very happy with our performances so far," he said.
"The most important thing was to strengthen our defence when I got here because last year we let a huge amount of goals in against us.
"And defensive work starts with me as a front man, so it’s always a lot of work, but I also respect that I have to participate in the defensive job as well.
"I already call Sydney home, so that means a lot. I’m feeling very happy in Sydney and I can already imagine staying a little bit longer."
