Jose Mourinho still has plenty of issues at Chelsea despite flying start to season

They may be Premier League leaders, but the number of goals they have conceded will be among the things their manager will want to see change.

Jose Mourinho and Chelsea were frustrated by their draw in midweek with Schalke. Ian Kington / AFP

It was in the equivalent fixture last February that Jose Mourinho enjoyed probably his finest moment since his return to Chelsea.

His side sat deep and they broke with a muscular energy. They won 1-0 and also hit the woodwork three times.

That success, with about three months of the season remaining, pulled Chelsea level with City in the table and two points behind the leaders Arsenal. It seemed then that they would win the title.

Eight days later Chelsea were held to a 1-1 draw by West Bromwich Albion, a sign of the inability to finish off lesser sides that would see them also drop points against Aston Villa, Crystal Palace, Sunderland and Norwich City before the season was out.

A few days after that draw at the Hawthorns, Chelsea returned to City in the FA Cup and were well beaten 2-0, although, with one eye on European commitments, both sides fielded slightly weakened sides.

Wednesday’s 1-1 draw against Schalke in the Uefa Champions League suggested Chelsea have not entirely overcome their issues against teams who sit deep against them, at least when forward Diego Costa is out of the starting line-up.

Mourinho acknowledged after that game that the Spain international cannot play three games a week but, although he came on with 16 minutes remaining on Wednesday, he should be available for Sunday, when he can build on an extraordinary record of seven goals in his first four Premier League games.

Costa’s presence against City is perhaps less significant than in other games. City are unlikely to sit deep. They will look to take the game to Chelsea in a way that Burnley, Leicester City and Swansea City did not.

Everton might have done but the way Chelsea shot into a 2-0 lead within the first three minutes made that game slightly freakish.

Almost from the off it was turned into a slugfest, won 6-3 by the visitors, as Everton desperately fought back.

That means there is likely to be space behind the City rearguard, particularly as the injury to Fernando means the option of 4-3-3 is effectively denied them. That brings the likes of Eden Hazard, Andre Schurrle and Willian into play.

The other issue for Chelsea, surprisingly, is their defence.

Impressive as they have been this season, Chelsea have let in six goals in four games and the question is whether that is down to a little laxity or whether there are structural problems within the 4-3-3 that top sides can ­exploit.

The battle between David Silva and Nemanja Matic, who has been excellent in pretty much every game apart from that cup match, is likely to be key.

This already feels decisive. Chelsea are five points clear of City, who are the closest of the sides who represent their likely rivals for the title. A win at the Etihad tomorrow and Chelsea’s lead will quickly begin to look insurmountable.