They are currently 10th in the Premier League, 10 points off the top four.
“Chelsea must consider their short-term future,” said Hiddink.
A year ago Chelsea were also out of the Champions League, but top of the Premier League on 63 points from 27 games as they cruised to a third title under Jose Mourinho.
The Portuguese has now been sacked and the Blues are 23 points worse off than on this date last year – despite having played two more games.
They last missed out on the Champions League in the 2002-03 season, after finishing sixth under current Leicester boss Claudio Ranieri.
“Chelsea are now in a transitional period and they now have to see how to go on to try to regain the lost terrain where they used to be,” said Hiddink, who will leave his post in May.
“It is difficult to get into fourth in the Premier League, but we knew that and we tried to do our first job, which was to get out of the relegation zone.”
Hiddink accepts Hazard jeers
Chelsea’s supporters gave Eden Hazard – who has been linked with PSG – a mixed reception when he limped off with a hip injury late on.
Hazard’s departure was greeted with jeers from some fans, another sign of his fragile relationship with Chelsea’s supporters, who were unhappy with his contribution leading up to the sacking of Mourinho in December.
The Belgium winger scored 19 goals last season on his way to winning player of the year – but has scored just twice in a hugely disappointing campaign.
Hiddink, who has major injury doubts over Hazard and goalscorer Diego Costa for Saturday’s FA Cup quarter-final at Everton, said: “The fans have the right to express their feelings. Hazard was also having a problem with his hip.”
The Dutch manager also disapproved of Hazard exchanging shirts with PSG’s Angel di Maria at half-time – although he insisted it was not a major issue.
He said: “I’m aware of it. In some countries they do it and I don’t want to see a bad thought about that or overvalue it. It’s not a big thing for me.
“I’m sure knowing those two players there was no bad intention there.”