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Guardian writers' predicted position: 1st (NB: this is not necessarily Paul Doyle's prediction, but the average of our writers' tips)

Last season's position: 3rd

Odds to win the league (via Oddschecker): 9-4

For José Mourinho to remain the Happy One he will have to make some people at Chelsea sad. How he deals with that will go a long way to determining whether the club can mount a credible Premier League challenge for the first time in three years.

Most Chelsea fans are understandably optimistic: Mourinho's Real Madrid reign may have been blighted by infighting but all the success he has enjoyed throughout his career, including during his last spell at Stamford Bridge, has been built on creating the smart battle plans and mighty esprit de corps that Chelsea lacked at crucial times in the previous two campaigns, their cup triumphs notwithstanding.

It is not totally clear whether Chelsea's squad is top-drawer or just top-shelf, since it looks obscenely over-endowed in some areas but suspiciously deficient in a couple of others. Mourinho will have spent the summer determining whether he needs to recruit to provide attractive balance or whether the two main zones of doubt – striker and defensive midfield – can be enhanced by tactical changes and emerging young talent.

At some point soon, Romelu Lukaku is going to have to be given a chance to prove he can be the main man in an elite team's attack. He has done everything that could be reasonably expected of him so far, including hitting 17 Premier League goals while on loan at West Bromwich Albion last term, which is more than Fernando Torres (eight) and Demba Ba (two) managed for Chelsea between them. The London club were the second-highest scorers in the Premier League last season but still suffered from the lack of a really sharp centre-forward.

Lukaku is faster, stronger and more deadly than that pair but, at just 20, he has not yet had the opportunity to confirm that he is savvy enough to lead a top team for an entire campaign. The bid for Wayne Rooney suggests Mourinho fancies having a more seasoned striker to call on (and hasn't lost his knack for mischief-making), which, if the manager is going to deploy a 4-3-3, means Lukaku may not start quite as much as he hopes, though he should probably still have a big role to play.

Certainly a bigger one than Ba and Torres, and the latter is unlikely to relish a back-up role, especially in a World Cup year, and may therefore be replaced if a buyer can be found.

The profusion of creative midfielders, which has been augmented by the signing of André Schürrle and the return of Kevin De Bruyne, means whoever plays up front is sure to be supplied with plenty of scoring chances. There is no reason to expect Juan Mata's form to be any less wonderful than it was last season while Eden Hazard and Oscar, being one season wiser and stronger, are likely to gain consistency. The puzzle lies in how Mourinho will seek to ensure midfield has solidity as well as invention. In several big matches last season, such as at Manchester City, Juventus, Shakhtar Donetsk, and Swansea in the Capital One Cup, opponents were able to play through them too easily.

Mikel John Obi, Frank Lampard and Ramires were not totally convincing when played deep; David Luiz looked to be the solution for a while but Rafael Benítez appeared to lose confidence in that ploy and, besides, the Brazilian may be better used further back.

This season Marco van Ginkel or the returning Michael Essien may provide the answer and Mourinho's familiar 4-3-3 may override any vulnerability in the middle. Given that the Portuguese has always liked to have a strong spine of the side to rely on, he may still buy a surefire fixture for central midfield, which would explain the reported interest in Sami Khedira.

Apart from those two areas, where Chelsea do not appear to have quite as much strength in depth as Manchester City, for one, Mourinho already has the personnel to succeed. Petr Cech remains an outstanding goalkeeper, Ashley Cole is still immaculate at left-back and César Azpilicueta showed last season that he is a fine right-back, both defensively and in terms of his attacking contributions. Chelsea have four good centre-backs, though John Terry will have to accept that he is the fourth best.

While Mourinho can be expected to ensure that Chelsea never seem as unbalanced as they sometimes looked in the past two years, it will be interesting to see whether he can do that while placing an accent on panache. What is certain is that under him Chelsea will pursue victories with more ferocity: last season they won the same number as points as Manchester United against teams in the top half of the Premier League but amassed 14 fewer than the eventual champions against teams in the bottom half – that was ultimately the margin between Chelsea and the title.

They dropped four points to Queens Park Rangers and Southampton in matches where their focus looked blurred, just as it did in the draw at Reading and the defeat at Newcastle. Mourinho will surely adjust that attitude. He is also likely to take more decisive action to influence matches that are not panning out as planned, partially because he will have more options on the bench than Roberto Di Matteo and Benítez had and partially because his substitutions are less formulaic than the Spaniard's tended to be.

Player focus infographic