West Ham manager Gianfranco Zola will order his side to target Chelsea's frailty at set-pieces as they look to kickstart their campaign with a home win against the Barclays Premier League leaders on Sunday.
The Blues have won just one of their five matches in December and their defence has come under the spotlight after conceding 11 times this month. A number of those goals have come from set-pieces, with goalkeeper Petr Cech coming in for some criticism for failing to command his box.
"We know that they have been conceding from set-pieces," said Zola, a former Chelsea player.
"We have been very dangerous from set-pieces ourselves so that might be the key to the game.
"Chelsea have lost a bit of confidence and I am not sure why, but I hope it continues. Chelsea are not the same Chelsea they were some time ago. But they are still top of the league and a fantastic performance is required from us."
Zola's defence has been even more porous, shipping 14 goals in their last six league games.
One of the goals they conceded in the 3-1 defeat to Bolton on Tuesday night came when goalkeeper Robert Green, who has been one of the Hammers' star players this season, inexplicably fumbled a straightforward shot at the feet of Ivan Klasnic, who tapped home.
Zola expects Green to bounce back against Chelsea in a match where the England custodian could be under severe pressure.
"Robert Green is a strong person, a strong man and he will be okay," Zola said. "He knows what he did and I didn't need to say anything to him. He has been magnificent for me since last year and he knows he made a mistake.
"It happened a couple of times with me - I missed chances without a goalkeeper in front of me from one yard out. It's part of the game."
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