Gary Cahill says Chelsea face the "ultimate challenge" when travelling to Premier League leaders Manchester City on Monday.
Chelsea on Wednesday night recorded a seventh clean sheet in nine games in all competitions in a goalless draw with West Ham which left Jose Mourinho so frustrated he described Sam Allardyce's tactics as from the 19th century.
City boast a 100 per cent record from 11 home games, scoring 42 goals in the process.
Gary Cahill told Chelsea TV: "They're banging goals in left, right and centre. It's going to be really tough. We had a really good result against them at home; away from home (at the Etihad Stadium) they've been so, so strong.
"I suppose it's the ultimate test. It's going to be a really, really tough game. We've got to try to look forward to those games and going there on Monday is exciting."