Chelsea can dominate for years to come, what more is needed?

Putting that into context, the £59m spent on the pair was £3m less than Arsenal paid for Alexis Sanchez (£30m), Danny Welbeck (£16m) and Calum Chambers (£16m). If hairs are to be split, the Blues also brought in Mario Pasalic, the same age as Chambers, for £2.4m, which more or less evens up spending on three players apiece.

Consequently, the Gunners currently sit eighth on 10 points, nine behind Chelsea, who also beat Wenger’s men 2-0 at Stamford Bridge recently; Fabregas playing a key part in the decisive goal. To further prove Mourinho’s instincts right, Costa leads the scoring charts with nine goals, four ahead of Argentine pair Sergio Aguero and Leonardo Ulloa, and Saido Berahino, while Fabregas is top of the assists table on seven.

Despite also bringing in talented left back, and Costa’s teammate from Atletico Madrid, Filipe Luis (£15.8m), plus former fans favourite Didier Drogba back to the club on a free transfer, and Loic Remy (£10.5m), there is the suggestion the blend in the striking department isn’t quite right.

A lot of responsibility rests on Costa’s shoulder, like Drogba in his prime, though the Brazilian-born Spain centre forward apparently has injury concerns. If they did lose him for even a couple of months, Remy would need to step up, or the ageing Drogba would need to re-discover the scintillating form of the past.

French forward Remy clearly has talent, and could be world class, though within the striking hierarchy perhaps a more established striker needs to be brought in who can competitively challenge Costa. Due to Mourinho utilising a one-frontman system, the problem is finding someone who would be content with spending spells on the bench who isn’t quite world class, though can offer the physical element.

Jackson Martinez, who flourished at the World Cup in scoring two goals for Colombia, currently plays for Mourinho’s former club Porto, and has consistently expressed his desire to ply his trade in the Premier League. At 28, he is at the right stage of his career to move on, and would suit Chelsea to a tee.

Already, he has nine goals in 11 games, across all competitions, including three in two Champions League matches. If Martinez wants to catch the eye, more of the same in Europe’s elite competition would surely convince Mourinho to make a move.

Perhaps what they also need is more of a driving force in central midfield; the box-to-box dynamism Frank Lampard used to offer in his pomp. Although Ramires is full of energy, he is considered quite lightweight for the Premier League, and has a rash streak that has made him a magnet for bookings and increases his chances of injury.

Recently, the Blues have been linked to Real Madrid’s Sami Khedira, who is thought be available for as little as £10m. Lining up alongside Matic, with Fabregas in front and Hazard and Andre Schurrle on the flanks, this would be a formidable midfield quintet. Mourinho then has the nice headache of trying to fit in Oscar’s work rate.

One sticking point is that Madrid are thought to want goalkeeper Petr Cech in return, who has lost his place to Thibaut Courtois. Chelsea, however, have proved over the past couple of years that they are a club to watch when it comes to negotiation, and could give Real a run for their money.

Added to the £37.1m they received for Mata, they sold Brazil defender David Luiz, who went onto flop at the World Cup, for £50m, as well as big Belgium frontman Romelu Lukaku for £28m. These deals financed their own outgoings for Costa, Fabregas, Luis and Remy.

The likelihood is that Chelsea will once again be successful in any new transfer dealings. They also currently have a raft of young talent they have accumulated over the years, out on loan that can be sold for huge returns.

Case in point; Lukaku. Roman Abramovich more than doubled his money on him. It is also reported that this process was repeated with Kevin de Bruyne. Their new business model cannot be argued with.

When John Terry decides to hang his boots up, they have Gary Cahill, who is gradually starting to look like a carbon copy of the 33-year-old for both club and country. Options are limitless and, with Borussia Dortmund’s German talent Mats Hummels courting interest from both Manchester United and Arsenal, previous form suggests if they Blues enter the race then those other suitors are in trouble.

They beat both teams, plus Manchester City to the signing of Eden Hazard, one that took many by surprise and established Chelsea once again as serious contenders. There is no doubt whether Hummels would suit Chelsea. Refined in style, comfortable on the ball and aerially dominant, he could slot straight in, though there is also Zouma ready to zoom off the conveyor belt.

Whatever happens at Chelsea over the coming seasons, they appear to be in great shape, and for the Champions League victory Jose Mourinho craves they are 6/1; though, it is perhaps a season too early. Just three more quality signings could change the shape of the Blues’ future, and leave a permanent smile on the face of “the Happy One”.