The Blues were held to a 1-1 draw by Steve Cooper's Reds at The City Ground, as Serge Aurier cancelled out Raheem Sterling's opener.

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• Azpi's Forest assessment

• Gallery: Working hard ahead of City's visit

Koulibaly, who was partnered by Thiago Silva in the centre of Chelsea's back four, gracefully admitted that Forest's second-half performance warranted them claiming a share of the spoils but refused to accept that the top four could be out of our reach.

'It's going to be a big challenge [to finish in the top four] but we like a challenge and we always believe in ourselves,' Koulibaly said after the stalemate on the banks of the Trent.

'We have to embrace it, we have to believe in ourselves and work hard to improve. We will get ready to face Man City, which will be a tough game but we will do everything to win this match and move forward.

'We're disappointed not to get the three points because we always go into games wanting to win.

'In the first half we did quite and looked in control but in the second half, they came at us with more aggression and more positivity in their play. Forest made things difficult for us, we couldn't keep a clean sheet and this was disappointing.

'It's a tough stadium to play at. They haven't lost here for a long time and they've already beaten some good teams here.

'We're disappointed because we want to win every game but we have to take this point and prepare now for Man City. We have to keep on working hard.'