Guus Hiddink says Chelsea's serious problems this season will not be fixed immediately.

New Chelsea boss Guus Hiddink has warned fans that appointing him as manager does not mean the squad has a quick fix to its recent problems.

The 69-year-old faces Watford in his first game back in charge on Saturday, after watching from the stands as Chelsea beat Sunderland 3-1 last week in the wake of Jose Mourinho's departure.

Hiddink, who led the club to the FA Cup in his opening spell at the helm back in 2009, reflected on the club's poor form prior to his arrival and stressed it would not be easy to turn the situation around.

He said: "If you look back a bit to last season where there was this huge success in winning the title then of course you go into the next season and you have your targets, your aims and your aims are the same. Getting the championship again, even though in the Premier League that is not easy, that was the main target. The other targets of course are to go into the Champions League and the FA Cup.

"But it is not easy to fix as sometimes after a championship you might relax a bit as a team and then you get a wake-up call from somewhere in September, but the situation is that they were down last week to one point off the relegation zone, which was frightening for everyone inside the club. It is not easy to say 'I am here and tomorrow the problem is solved'."

Nevertheless, Hiddink revealed he was impressed by much of what he saw from his new players against Sunderland.

"I was in the stand and of course I saw the game and they were playing in a way in general like they enjoyed it very much," added the former Netherlands boss.

"There were some sloppy moments in the first 45 minutes and then sometimes they even went a little bit over the top and didn't kill it off after going 2-0 up but it was good to see how they can play – the quality is there."

The Dutchman did not rule out the prospect of Chelsea finishing in the top four, but suggested it was a tough ask given the how open the Premier League has been this season.

"Mathematically it is possible, if you can add up then it is possible but this league is very strong," said Hiddink. "That has been especially proven this year with all respect to the clubs at the top - Leicester, Crystal Palace, Watford - it is amazing and refreshing.

"It means that all the teams can kill each other."