The first thing to acknowledge is that there is time for Chelsea to make a success of this transfer window. It is the first week in July, not the last in August. Those within the club’s recruitment department can justifiably point to the late arrivals of David Luiz and Marcos Alonso last year, and the impact both players had on the team’s title success, as evidence that significant additions can be plucked from the ether right up to the cut-off.

And yet, not for the first time, they have made a rather undistinguished start in attempting to capitalise upon their status as champions. Suggestions Romelu Lukaku had broken off from a holiday to undertake a medical overseen by doctors dispatched by Manchester United to the University of Los Angeles, such a favourite pre-season training haunt of José Mourinho’s teams over the years, left the striker’s suitors in London winded. Perplexed even. All summer the assumption had been that the Belgian’s innate desire to return to Stamford Bridge would be key to securing him from Everton.

But somehow, maybe as a result of complacency on Chelsea’s part, or, as the club would have us believe, upon the advice and influence of the player’s agent, Mino Raiola, they have been bypassed.

There may be public attempts to deflect blame for this failure this failure over the weeks ahead, and an insistence that the man they do end up signing for a huge sum to replace Diego Costa – Real Madrid’s Álvaro Morata, Andrea Belotti from Torino, or even an Alexis Sánchez or Sergio Agüero from a direct Premier League rival – had always been their first choice. But the reality is Antonio Conte had been pinning his hopes on Lukaku leading the line.

Those reports in Belgium, that the Chelsea manager had been in regular contact with the Everton forward over recent weeks detailing his tactics for next season and making plain just how key he considered Lukaku to his game-plan, have never been contested. The player himself expected to return to south-west London. The manager anticipated welcoming him back into the fold.

Now Conte will stride back into his office at Cobham on Sunday infuriated at Raiola’s influence but also demanding an explanation for the board’s apparent inertia over recent weeks. Sources in Italy, while aware the manager is distinctly unimpressed with the summer’s business to date, do not believe his sense of exasperation will prompt a resignation. Indeed, he is understood to blame the agent and Lukaku himself for their defection. Yet the Italian’s contract extension which has been on the table for months remains unsigned. Neither will he be appeased by the club permitting him to add Davide Mazzotta, his opposition scout with Italy at Euro 2016, to a coaching staff shorn of Steve Holland. Instead, he will require answers.

Why was a bid for Lukaku, a player the manager had made clear should be targeted, never submitted to Everton?

Why was a formal bid for Lukaku submitted so belatedly to Everton and at a value effectively well below that proposed by United? Why, for that matter, is Willy Caballero – a reserve goalkeeper secured under freedom of contract following his release at Manchester City – still the only player added to the champions’ squad? What is the hold-up with the medicals delaying the arrivals of Tiémoué Bakayoko from Monaco and Antonio Rüdiger from Roma? And the state of play on negotiations for Alex Sandro at Juventus? Big-money transfers can be tediously protracted and complicated but it is too simplistic to suggest the club are waiting to shelve the old Adidas training gear and parade an array of signings in glittering Nike kits.

The manager had hoped the bulk of the buying would be achieved early so he could fling them into the gruelling routine of double training sessions, and settle them into a squad who depart for a three-game tour of China and Singapore on 18 July. Some should have arrived by then – Bakayoko and Rüdiger are close – but the prospect of Chelsea departing for east Asia with Michy Batshuayi, a bit-part player last term, as their principal forward is suddenly very real. The manager bears some blame given his rash text to Diego Costa, subsequently made public by the disaffected striker, indicating the Spain international has no future at the club. The player, who scored 20 top-flight goals last term, has started bidding farewell to his club-mates and if, as anticipated, Atlético Madrid submit a first formal offer for him over the next few days, he will most likely be absent on Monday, when the rest of the first team return to Cobham.

Romelu Lukaku, centre, here in action against Manchester United, had expected to return to Chelsea. Photograph: Shaun Botterill/Getty Images

Chelsea were dismayed about Conte’s text message last month, not least because it wrested away a modicum of control that they might have had over determining Costa’s future. Maybe they have been awaiting the striker’s departure before actively moving for a replacement. Yet that SMS exchange served to expose the tension which has always been there, to a certain extent, between manager and hierarchy.

For all those late successes in securing players at the end of August last year, the Italian had cut a frustrated figure through most of the summer transfer window. Likewise, he had hoped his mid-winter business would amount to more than merely welcoming back Nathan Aké from a loan spell at Bournemouth. Now he returns to find a squad trimmed of John Terry, Asmir Begovic, Aké, Bertrand Traoré, Christian Atsu, Dominic Solanke, Kasey Palmer and Tammy Abraham – admittedly, by no means all senior players in the manager’s immediate plans – with considerable strengthening required.

It can still be achieved. Break the club’s transfer record to secure Sandro, and then sign a Morata, Belotti or Sánchez, and the manager may be appeased. Yet, until that is achieved, the suspicion will nag that Chelsea are allowing momentum to drain away yet again.

It happened in 2010 after Carlo Ancelotti’s Double-winning first season at the club, when they waited until January to secure the arrivals of Fernando Torres and David Luiz, first time round, to build on previous success. Then there was the summer of 2015 when Mourinho was dissatisfied with Pedro as his main addition. That was the close season when money was lavished on Baba Rahman, and relative small change spent on Papy Djilobodji and Michael Hector. It was hard to escape the sense that eyes had been taken off the ball.

That cannot happen again. Conte would not tolerate such a strategy, particularly with a return to the Champions League ahead. He hopes to challenge in that competition, not merely make up the numbers. Lukaku may have eluded them, but Chelsea must still make the market their own. For Marina Granovskaia and Michael Emenalo, there is much work to do.