GARY CAHILL believes Chelsea face the ultimate challenge when travelling to prolific 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.
The Hammers conceded nine goals to City in the two-legged League Cup semi-final, yet showed a defensive resilience against Chelsea which saw Mourinho's men concede two points in the title race.
City, who Chelsea beat at Stamford Bridge in October, boast a 100 per cent record from 11 home games, scoring 42 goals in the process and overtook Arsenal in the standings by winning 5-1 at Tottenham on Wednesday night.
Monday's contest at the Etihad Stadium will be a battle of the league's most miserly defence and the most prolific attack.
Cahill said: "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."
Chelsea have beaten City, Manchester United and Liverpool at home, while recording away draws at Old Trafford, against Tottenham at White Hart Lane and at the Emirates Stadium.
Mourinho, whose side also travel to City in the FA Cup, would perhaps be happy with another draw, but midfielder John Obi Mikel is optimistic of more.
"We have to have the belief that we can go there and win, that we can go there and play the way they play," Mikel said.
Mourinho believes he has completed his business for the January transfer window, unless exceptional circumstances dictate otherwise.