Rafael Benitez concedes the task of reviving Chelsea could turn out to be a bigger challenge than he had envisaged in the wake of his side's 3-1 defeat at West Ham United.

After little more than a week in charge, Benitez has overseen two scoreless draws and an unexpected reverse that has left the club's Premier League title ambitions severely dented.

That run has done nothing to get those supporters disgruntled by the dismissal of Roberto Di Matteo and opposed to the appointment of Benitez onside, and the reaction of the visiting fans at Upton Park confirmed the strength of feeling against the new manager.

Benitez's focus now shifts towards Wednesday's Champions League meeting with Nordsjaelland, a game Chelsea must win if it is to have any chance of progressing to the knockout stages of a competition it won last season.

To have any chance of securing victory against the Danish side, the interim manager must lift the spirits of a team that capitulated alarmingly against West Ham on Saturday after establishing a first-half lead.

Asked if he considered the job more challenging than he expected when he accepted the offer to replace Di Matteo until the end of the season, he said: "Could be. It's a top side in the middle of the season, and things aren't the best. We'll try to improve things, but it will take some time."

The difficult start has inevitably raised questions about Benitez's future, even after such a short time in charge.

But he said: "My concern is improving the team. If we do that, and start winning games, we'll be able to turn things around. The main thing for me is to improve the team. I'm not thinking about anything else."

And he insists he has the support of the players.

"After one week, I'm 100 percent sure they want to improve and want to win," he said.

West Ham was transformed after the break, clinching victory through goals from Carlton Cole, Mohamed Diame and Modibo Maiga, and sparking an angry reaction from Chelsea's fans.

Benitez said: "We have to improve on the pitch and the fans will be happy."