Jurgen Klopp's complaint over the Premier League start date is sure to infiltrate the season opener when Liverpool entertain Norwich City on Friday.

A combination of Copa America and Africa Cup of Nations commitments robbed Klopp of several stars for much of pre-season, leading the Reds boss to call for the English football calendar to be pushed back.

As the minutes tick down to that first whistle at Anfield, managers will be monitoring the condition of their players and making calls on fitness.

Do those in charge of globe-trotting squads have reason to fear sluggish starts, or can players push past heavy legs to set the league alight in the early weeks?

To consider the question, we have mined the Opta data to assess how three high-profile stars fared at the outset of the two seasons either side of last year's World Cup.

 

No concern over Kane

Harry Kane recently told reporters he feels as sharp as he has "for a long while" after a rare, relaxing off-season, which some view as the gateway to a fast start for the Tottenham striker.

Yet even in the aftermath of last year's long and emotionally exhausting run to the semi-finals in Russia, the England captain seemed to have no trouble getting right back up to speed for Spurs.

Kane scored five times over the course of the opening seven games last season, second only to a player he faced in the third-place play-off at the World Cup: Eden Hazard.

The haul was one fewer than he managed in the same period in 2017-18, which followed a tournament-free off-season.

Fitness did become an issue for Kane as a long 2018-19 campaign wore on and his workload for club and country warrants close inspection, but a longer holiday did little to boost his numbers at the beginning of the season.

Of course, not every player returned from the World Cup in the same psychological state as the tournament's Golden Boot winner.

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De Gea better for the break?

David de Gea was simply not himself last season.

Confidence sapped by a poor World Cup, the Spain star dipped well below his usually impeccable standards back at Old Trafford and might have lost the number one shirt had Sergio Romero not suffered ill-timed injuries.

Ole Gunnar Solskjaer ultimately kept faith with Manchester United's first-choice keeper and can reasonably expect a rejuvenated De Gea to make the kind of solid start to the season he enjoyed in 2017-18.

Then, the former Atletico Madrid man posted a league-high save percentage of 88.2 through to the end of September.

Fast forward 12 months and, with international matters perhaps still on his mind, De Gea did not rank in the top 10 for that statistic across the same period.

Poorer save percentages plagued other Premier League goalkeepers in the immediate aftermath of attending the World Cup.

Manchester City's Ederson, Mat Ryan of Brighton and Hove Albion and Leicester City mainstay Kasper Schmeichel all failed to meet their respective averages after travelling to Russia.

The latter, like De Gea, failed to claw his way into the Premier League's top 10 over the first seven games last term.

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Silva sets elite standard

As other players endure peaks and troughs, David Silva simply gets on with sustaining a level of excellence even in his advancing years.

The experienced midfielder started in Manchester City's triumph over Liverpool in the Community Shield last weekend and deserves a good deal of attention when the champions travel to London Stadium on Saturday.

Silva started the 2017-18 season in sublime style, registering a league-high six assists in the space of seven games and creating 23 chances in total – only team-mate Kevin De Bruyne (24) managed more.

He went on to win the title, attended the World Cup, and eased back into the Premier League by creating 20 chances before the end of September last season, more than any other player. All without real time to pause.

Could the 33-year-old help City set the pace yet again? West Ham would be safe to assume so: Silva has scored in four of his past five matches against them in all competitions.