LONDON • Pep Guardiola's challenge can be crystallised into a simple question: Will the manager allow Manchester City to defend this season?

The Spaniard endured an underwhelming, trophy-less campaign in his first season in English football. But his transfer activity since suggests that he is taking steps to address some mistakes.

He has realised that simply keeping possession and looking for openings may not always suffice in the high octane environment of the Premier League. So he has assembled a squad with many more facets for opponents to contend with.

Energetic full-backs have become increasingly important and City acted swiftly to bolster their ranks.

Out went the ageing Pablo Zabaleta, 32, Bacary Sagna, 34, and Gael Clichy, 32, and in came about £120 million worth (S$212 million) of full-backs in Danilo, Kyle Walker and Benjamin Mendy - giving City a different dimension altogether.

"With all respect to the players, last season, we were one of the oldest teams in the league. We didn't buy full backs for five, six years," said Guardiola, whose transfer business so far has lowered the squad's average age from 28 to 25.

"We decided last season we could change the team to make the team younger for the next four or five years. Danilo is 26, Mendy is 23, Bernardo (Silva) is 22, Ederson is 23, so we bought players who are going to be stable for the next years."

Guardiola could go with two up front to get the most out of Danilo, Walker and Mendy in a 3-5-2 system. He has already tested out a three-man defence in pre-season, with John Stones lining up alongside Nicolas Otamendi and captain Vincent Kompany.

Playing three at the back may also enable Guardiola to have both Sergio Aguero and Gabriel Jesus in attack, after generally using one striker last season following the latter's arrival in January.

Yet the prime error last term - when City finished 15 points adrift of champions Chelsea in third place - was an unbending emphasis on attack.

City managed only 12 clean sheets, five behind the division's best total, achieved by Manchester United and Tottenham.

Guardiola has moved to solve his problems at goalkeeper and full back yet there is still an issue in central defence.

The replacement of Joe Hart by Claudio Bravo, which subsequently backfired, has been addressed in the £34.7 million signing of Benfica's Ederson.

But as it stands, only centre-backs Kompany, Stones and Otamendi remain from last season's defensive line. Given the former's history of injury and the other two's thus far unconvincing City careers, there is a need to strengthen in that position.

Beyond the trio, Guardiola has only the untested 19-year-old Tosin Adarabioyo and the unwanted Jason Denayer and Eliaquim Mangala, following Aleksandar Kolarov's departure for Roma .

Real Sociedad's Inigo Martinez, who has a reported €30 million (S$47 million) release clause, is a defender being considered.

Yet despite the £158.2 million spend to rebuild the defence, the question remains: How much of the nitty-gritty of preventing goals will City's rearguard be able to do?

Guardiola, after all, asked, 'What are tackles?', following the reverse at Leicester last season.

His attack-at-all-costs philosophy will demand the pace of Walker and Mendy be harnessed by bombing into the opposition's half, which will leave City open to counter-attacks, as it did against many opponents last season.

Danilo can fill in as a holding player but is no specialist, so beyond Fernandinho, City are light there, as Guardiola's other headline buy was Monaco attacking midfielder Silva for £43.6 million.

To splurge £201.8 million in the window and not add a high-end defensive midfielder further points to Guardiola's priorities.

If Arsenal's Alexis Sanchez - who remains a target - arrives, then Real's record £218 million transfer spree of 2009 will be eclipsed.

But whatever the end total and tactics employed, Guardiola has to turn the title favourites into title holders. And he knows it.

"At Barcelona or Bayern Munich, there you have to win by far. If not, they don't give you a second chance," he said of his former clubs.

"But here, we have a second chance and we will try to do it better than this season."

THE GUARDIAN, AGENCE FRANCE-PRESSE, REUTERS