The world number nine, who has failed to match expectations in Australian tournaments, lost 7-6 7-5 to the Swede five weeks after ankle surgery and only a fortnight before the Australian Open.
"Just really disappointed again, leaving Brisbane so early," Stosur told reporters. "I think it was some good tennis and some pretty average tennis at times."
Stosur said the surgery and the subsequent shortage of training had not played a part in her defeat.
"I wasn't going into the match thinking 'Oh my God, I haven't done this or that'," she said.
"I gave myself every opportunity to try and play as well as I could but for sure, I have not practiced enough.
"I guess going into the match you want to think that that's going to be enough, but I think tonight it probably showed that it certainly wasn't enough.
"I have a fair bit of work to do ahead of me. You could put it down to being a bit rusty and it's the first match."
Saturation media coverage and public expectation is again accompanying Stosur's attempt to add the Australian Open to the U.S. Open title she secured by upsetting Serena Williams in 2011.
"I don't know how much of that really played into it," she said. "I've said it before, it's great playing out on a court where you've got the crowd behind you and trying to cheer you on and all that."
Stosur's last tournament before the Australian Open starts in Sydney on Sunday.
"I know that panicking doesn't help anyone get a good result or feel better," she said. "There is no magic dust that's going to make anything go away or fix it overnight or anything. I'm not the first player to have their home grand slam and not perform.
""There has been a few Australian and French players, you name it. It's a tough thing.
"Again, would I rather have a grand slam in my country than not? I would.
"All you can do is try and play your best. I know that people believe in me and what I'm trying to do are the right things. You just really want to perform right here, right now. That's what I'm going to keep trying to do."
(Editing by John Mehaffey)