Interim manager Guus Hiddink says Chelsea have to improve in order to pull themselves to safety in the Premier League. Since the Dutchman replaced Jose Mourinho, Chelsea have won once and drawn twice, but still the champions sit in 15th place, three points above the relegation places.

I didnt want to know a lot from the past but its obvious that we have to improve, he said. We start gathering a few points and it was the third consecutive game that Chelsea didnt lose. But thats not enough.

I think that Chelsea must now come into a winning period of games. Thats important. But you see how it is. All the big teams, they lose points as well. Arsenal is losing points against Southampton, Leicester is doing well, keeping up, so nowadays its very difficult. And if you see where our next opponent (Crystal Palace) is in the table, they are close to the Champions League positions. They are defensively very well-organised with just 16 goals conceded so far. So its not that easy nowadays to go into a long-term winning sequence, but we have to go there, Hiddink insisted.

With reports that midfielder Cesc Fabregas was unhappy, Hiddink brushed aside rumours that any high-profile players would be leaving the club in the January transfer window. I think we need all the players until the end of the season. You know better than I do that Chelsea was in a position where they have to improve a lot to go up the table, and we need all the players for the moment, he said.

So we dont talk and we dont go into rumours wherever they come from. Asked whether Fabregas was happy, he replied: Yeah, he is coming in with a smile and thats what I always like, when players come in with a smile and not with a worn-out face.

Hiddink refused to speculate on what role legendary former striker Didier Drogba would fill if he were to return to the club from MLS club Montreal Impact. Drogba, who watched the win over Sunderland alongside Hiddink and owner Roman Abramovich, is believed to have been offered a role at the club as either a coach or a club ambassador. Well it depends also on the player himself, he said. I think you should give them time and opportunities to find out what the best is for them. It might be in the coaching staff, it might be ambassador.

I think those guys they need to go into the squad and help younger players, old players with their huge experience. So Im not in favour of a big ambassador travelling around the world in a tie, thats what I dont like. I think they must give their huge experience to especially the young kids and helping out the older ones when there is some trouble.

Chelseas next game is against on Crystal Palace on 3 January. Palace are 11 points and 10 places above the Blues in the league.