Whoever the next Chelsea manager is, they will have to change a lot of things. Their whole team needs refreshing.

Whether big names like John Terry, Eden Hazard and Diego Costa leave will be his decision but, even if they stay, Chelsea need to regroup in the summer and buy a lot of new players.

Interim boss Guus Hiddink has had some good results since he took over from Jose Mourinho just before Christmas but their season is now effectively over following their exit from the Champions League and then the FA Cup this week.

They remain unbeaten in the Premier League since he took charge but I still don't think Chelsea have really clicked under Hiddink, who has the job until the end of the season.

They have not been fluent for some reason and it was the same when I saw them lose to Everton at Goodison Park on Saturday. They were not good enough.

I look through Chelsea's squad and think they should be a great team but, even when they win under Hiddink, they are still a little mechanical and are missing a bit of flair.

I think this is why the board wants to try something different with their next manager, which is the main reason they have not given the job to Guus permanently. I think he wanted it, because he loves life in London.

Hiddink denied another fairytale finish

I played briefly under Guus when I was a young player - and when he was a young coach - starting out at PSV Eindhoven in 1987. We get along very well. Since then he has developed his way of coaching and he has had a great career.

There have been ups and downs, of course, and he has not had a great time since his last spell at Chelsea when he won the FA Cup in 2009, but anyone who has spent as long as he has in the game would be the same.

His strengths are that he is an excellent man-manager. The main thing with him is that he knows how to deal with good players, to motivate them and make them feel right.

Tactically he is versatile. He plays on the strengths of the players he has got, which is why he has done a good job since coming back to Stamford Bridge to take Chelsea up the Premier League table.

Jose Mourinho's teams always play the same way but I would not look at a Hiddink side and say that. His style is far more adaptable.

At Chelsea, it had been working pretty well until this week, when I felt they lacked aggression going forward against Paris Saint-Germain on Wednesday.

If you don't put your opponents under pressure then they get more and more confident, which is exactly what happened at Stamford Bridge.

Going out of the Champions League meant the FA Cup was very important to Hiddink - he would obviously have loved to have signed off with another Wembley win.

Instead, Romelu Lukaku's goals mean Chelsea must look ahead to next season - and how they can improve.

What next: Conte in, Terry out?

It was a surprise to see Antonio Conte linked with the Chelsea job - and until he is appointed nothing is definite - but the newspapers say the Italy boss is the big favourite to take over after Euro 2016.

If it is Conte, his first job will be to get Chelsea back into the Champions League, because that will be a big miss for the club next season. It will not be easy.

Last time Hiddink was in temporary charge, in 2009, Carlo Ancelotti came in next and did a great job.

Ancelotti won the Double in his first season but things were a bit different then - the Chelsea squad looked more balanced and had more quality, and the likes of Petr Cech, John Terry, Frank Lampard and Didier Drogba were at the very top of their game.

John Terry's Chelsea fact file

This time, the new manager will also have some fantastic players but there are some question marks over what the future holds for the likes of Hazard, Costa and Terry - in his case, because of his age.

I said at the start of the season that I thought Terry was still Chelsea's most important player because a good foundation is the most important thing for any team.

We have seen that is true because of the way they struggled when he was out of sorts earlier in the season.

So I am curious about what will happen with Terry next, and whether he will get a new contract.

I understand he is 35 but he has a very important impact not just on the pitch but also in the dressing room and as a link to the fans. Surely he still has a part to play.

Ruud Gullit was speaking to BBC Sport's Chris Bevan.