The disastrous start to Chelsea's 2015/16 campaign took another debasing hit last night as Jose Mourinho's muddled Blues found themselves at the end of a 2-1 defeat to his former club - Champions League Group G opponents FC Porto.

The Portuguese outfit are a decent side and compared to some of the Premier League's other European nightmares in recent weeks, PSV's win over Manchester United for example or Arsenal's back-to-back defeats to Dynamo Zagreb and Olympiacos, the Estadio do Dragao affair was by no means the most disconcerting.

Yet, when coupled with domestic woes, last night's result makes it five defeats in eleven across all competitions for the Premier League champions this season - a harrowing run few could have envisaged when the Blues thumped Porto's Primeira Liga foes Sporting Lisbon 3-1 to round off the Group Stages last December.

The Chelseas of last term and this season are almost incomparable. The former, a title-winning outfit spawned from experience, industriousness, defensive resilience and attacking quality; the latter lumped with the second-worst goals conceded record in the Premier League, seemingly devoid of all structure, organisation and appetite for victory - even if a few glimpses of that final third proficiency remain.

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Although the ultimate cause of Chelsea's sudden decline has reached no unanimous verdict, many trace it back to the Blues' limited activity during the summer; Jose Mourinho's one-in-one-out policy and the west London outfit's failure to sign the two prodigious talents at the top of their wish list, Everton's John Stones and Juventus' in-demand midfielder Paul Pogba. The Blues would certainly have jumped up a level from last season if both were effectively integrated into the starting Xi.

I too see many of Chelsea's problems stemming from the transfer window, but it's the players they lost rather than those they failed to sign that have impacted most on their recent form - namely, Didier Drogba and Petr Cech.

They didn't seem like debasing departures at the time, having made a combined twelve starts out of a possible 72 in the Premier League during their final campaign at Stamford Bridge. Last term's top scorer Diego Costa was drafted in as the Drogba of Mourinho's second spell, seemingly sharing his physicality, aggression, gamesmanship and desperation for victory, whilst Cech left for Arsenal after losing his No.1 jersey to Thibaut Courtois - the 23 year-old prodigy already regarded as one of the world's best goalkeepers.

Yet Cech and Drogba are Chelsea men through and through, boasting 867 appearances between them. If the Blues' history started in 2004 as rival fans often jest, then the pair have been at the epicentre of every chapter of the Chelsea narrative; present for all four of their Premier League titles and integral contributors to the 2012 Champions League crown. The former holds the record for most clean sheets in the club's history; the latter was voted the club's greatest ever player.

Perhaps more importantly, they're Mourinho men through and through, having arrived during the Special One's first summer in west London to become integral bookends of the Chelsea side he lead to consecutive league titles.

They were leaders of the dressing room, vice-captains for the Blues and skippers of their national sides, walking effigies of the club's past and identity, vastly experienced and fully aware of not only what it takes to win silverware, but what it takes to win silverware in a Mourinho side. Eleven games on from their departure, it's quite clear a void has been left behind.

I have no doubt Mourinho anticipated such a scenario, having expressed on countless occasions his desire to keep both at Stamford Bridge for another year. What will have shocked the Portuguese this season, however, is how more senior members of the squad have failed to answer the challenge of filling Cech and Drogba's shoes.

Chelsea's squad is the sixth youngest in the league, with an average age of 26, but it boasts plenty of experience through the likes of Nemanja Matic, Cesc Fabregas, Radamel Falcao, John Terry, Pedro, Ramires, Gary Cahill, Branislav Ivanovic and John Obi Mikel, all of whom are 27 or older and have proved their pedigree at top level. Likewise, although Eden Hazard is just 24, he's already acclimatised with leading by example as Chelsea's and the Premier League's flag ship talent.

Paradoxically, many of those are amongst the biggest culprits behind Chelsea's poor results in terms of individual performances, which eats away at any dressing room authority they may wish to impose. Some dynamics of the group have clearly changed. They seem more uneasy with each other, as if nobody is quite sure of who the leaders truly are - something Chelsea's chaotic defending in their last two games paid specific homage to.

Does that add to the argument of reinstating Terry after spending four of the last five games on the subs bench? Perhaps in the short-term. Joe Cole once quipped 'Chelsea play 10% better with John Terry in the side' and I still think that's largely true, albeit perhaps less consistently than we've become accustomed to.

But the Blues skipper will have turned 35 by the end of the season and Mourinho quite clearly feels his strengths no longer justify his weaknesses to the extent that he starts every game. The former England international could well call it a day next summer - so where would Chelsea's leadership come from then? Suddenly, the Blues are stuck facing the same dilemma that's currently corroding their form.

Over the next few weeks, it's vital a leader emerges from the shadows - someone prepared to play without fear, make their voice the loudest in the dressing room and with the ambition to eventually succeed Terry as captain. Judging from their recent performances, however, none of the Chelsea squad are ready for that responsibility just yet.

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