LONDON • The mere mention of a title defence has been enough to drain the optimism from Chelsea managers of the recent past.

It is as if a malaise creeps in unnoticed with the hangover from all the ticker-taped celebrations, indecision bordering on complacency gripping those from dug-out to boardroom over the subsequent summer.

Inertia chokes plans for recruitment, while players who had previously been focused in pursuit of the Premier League title suddenly struggle for motivation when asked to repeat the feat, which Carlo Ancelotti experienced in 2010. Jose Mourinho followed suit five years later. Antonio Conte is braced to be next.

Chelsea, as a club used to enjoying regular success, were scarred by their mid-table finish two seasons ago in particular. They vowed such underachievement would never be tolerated again.

So the trials and tribulations endured this summer feel all the more remarkable: From the messy attempts to sever ties with Diego Costa, to the frustrations expressed by the management at the club's failure to secure Romelu Lukaku; from the hierarchy's laboured efforts to add to Conte's options before a return to the Champions League, to a rather chaotic pre-season schedule.

"We know it will be difficult next season, and we will try and avoid what happened to Mourinho's side at the start of 2015," Conte said.

"Two years ago, Chelsea finished 10th and that cannot happen again."

However, planning for the campaign ahead has been far from straightforward.

There have been tensions behind the scenes. Conte did finally put pen to paper on a new two-year contract last month, but it was only a reward of a better deal and not an extension of his stay at Stamford Bridge.

In maintaining the original length of the arrangement perhaps the hierarchy, too, demonstrated lessons have been learnt, not least from the hefty deal delivered to Mourinho in the autumn of 2015.

In Conte's view, caution was his priority and he prefers to take things step by step. The positive soundbites offered up by the manager have always been issued with a warning.

Winning a Premier League crown without European football cluttering up the schedule is one thing. Competing for silverware on four fronts is quite another.

"I repeat, we are a great club but we are in a moment where we can't make a mistake because it's very dangerous," the Italian said.

"We don't have a lot of space to make mistakes. We need to improve and increase our squad to be something important for the present, and also for our future."

That quest to add greater quality to the squad is ongoing. Before a more onerous fixture list this season, Chelsea have seen Oscar, Branislav Ivanovic, John Terry, Nemanja Matic, Nathaniel Chalobah and Nathan Ake leave, with Costa to follow suit.

Throw in the fact that Eden Hazard and Tiemoue Bakayoko are recovering from surgery, which will blunt their impact at the start of the season, and the Italian's consternation at fragile options feels more understandable.

So, assessing whether Chelsea will boast the required depth to retain their title is probably best put off until next month, when the transfer window has closed.

Should the club successfully pursue players such as Alex Sandro, Antonio Candreva and Fernando Llorente - the latter would be a back-up option - or even Virgil van Dijk, then their challenge would feel more persuasive.

Bakayoko, once fit, and Antonio Rudiger should prove astute additions. Alvaro Morata, a striker courted last summer, may still prove a more effective replacement for Costa than Lukaku might have been.

Whether the Spaniard can match Lukaku's 25-goal return in the season ahead is still open to question, but Conte has been waiting to work with him ever since signing Morata for Juventus in 2014, just before his appointment with Italy.

The striker will provide a mobile target across the frontline and, with Michy Batshuayi impressive in pre-season after last term's bit-part role, it will be intriguing to see how Chelsea evolve post-Costa.

Where the team had arguably stagnated under Ancelotti and Mourinho when it came to defending their title, Conte gives the impression he can tweak and innovate, adapt and reinvigorate.

He caught the division on the hop with his tactical switch last season, but he may not rely entirely upon a 3-4-3 in the campaign ahead.

The mantra of "work, work, work" will remain, and the core will know better what to expect this time round.

Chelsea should rejoice in the 48-year-old's restlessness over the summer. They can point to that as evidence of the perfectionist in him, a manager who will not be lingering on last season's success but has recognised maintaining high standards of success in the campaign ahead will prove far trickier.

Conte will be determined this season's defence proves more productive than in 2010 and 2015. If he is given the tools with which to work, history should not repeat itself.

THE GUARDIAN, REUTERS