Interim Chelsea manager Guus Hiddink believes his replacement will have a massive task ahead of them to rebuild the squad and be capable of challenging Europe's elite once again.
Chelsea are 12th in the Premier League table - 14 points outside of the top four - with Champions League qualification for next season seeming increasingly unlikely.
Hiddink, who took over from Jose Mourinho on a short-term basis after the Portuguese departed in December, thinks Chelsea have fallen behind the biggest club's in Europe.
And the Dutchman has warned his successor that the rebuilding job at Chelsea will not be an easy one.
"It's not a small job," he said. "I don't want to open up too much but everyone has to make good analysis about the strength of the squad, about the weakness of the squad, and accordingly they have to react in building up, or making the squad stronger for next season. That's not a small job.
"I don't want to go into details. I am here in the interim period and the people who are not responsible for the every day, every week stuff and games, they have the longer vision of what is the need of this club, they are in charge to do that."
Hiddink said he now sees a big gap between Chelsea and the elite European clubs such as Barcelona, Bayern Munich and Paris Saint-Germain.
"If you look at the potential of clubs like Barcelona and Bayern Munich, it is huge," he said.
"To be honest, if you see PSG, they have a very strong, not just first 11, but can go on to 15, 16, 17 big players.
"We had some youngsters on the bench against PSG. I am not scared to bring them in but in the long run of a lot of games, you need a bench which is also very experienced."