Chelsea sit 15th in the Premier League after 17 games, just three points above the drop-zone.
Hiddink added that finishing fourth was still a “mathematical possibility” but said it would be a very difficult task.
“This league is very strong,” he said. “All the teams can kill each other.”
“I shouldn’t be here halfway through the season. It means things are not going well. But, anyhow, I am glad to be back. It is a few years ago I was here in a similar situation.”