There is not too long to go now before the Premier League returns, and teams have started to report back for pre-season.
Some clubs have completed big money signings, such as Liverpool bringing in Fabinho from Monaco and Manchester United capturing Fred from Shakhtar Donetsk, but the majority of teams are holding off from doing their key transfer business until after the World Cup.
While teams will be working hard to complete incoming transfers, they will also not want to lose the key players they already currently have on their books.
But who are these key players? talkSPORT have taken a look at every Premier League squad and have selected the one player every every club cannot afford to lose this summer.
You can see the list below...
Arsenal - Granit Xhaka
The 25-year-old Swiss midfielder has polarised opinion at the Emirates with inconsistent performances that didn't live up to his £34m price tag, despite appearing in all 38 Premier League matches last season. But with the exit of Jack Wilshere, Xhaka has an opportunity to blossom in the Arsenal midfield as he reaches his peak - as demonstrated by his exemplary performances for Switzerland in the World Cup. Known for his hit-or-miss shots from distance, his 30-yard laser effort against Serbia reminded Arsenal fans why he is a necessary presence. New Gunners boss Unai Emery feels the same, having rewarded him with a new long-term contract before he jetted off to Russia.
AFC Bournemouth - Josh King
In 2016/17 the Norwegian scored 16 goals in 36 matches during a breakthrough campaign, but the 26-year-old has expressed frustration at how manager Eddie Howe has used him as an attacking midfielder, rather than a striker, in a season where he was limited to eight league goals. Newcastle have been linked with King, who has three years left on his contract at Bournemouth. Howe admitted the Cherries depend on him, but it's likely he will have to move King back to his preferred position to ensure he stays on the south coast.
Brighton & Hove Albion - Shane Duffy
The towering defender was voted Ireland's Senior Player of the Year after becoming a mainstay in Chris Coleman's side. At Everton, he would shake with nerves at the start of matches, but he has matured into a key member of the Brighton set-up, one willing to take risks while making increasingly more measured decisions.
Burnley - Nick Pope
Pope has come a long way since he was released by the Ipswich Town academy at 16. Through eight loan spells to starting last season as number two to Tom Heaton, Pope has prospered in his breakthrough season and is now in Russia with England for the World Cup. He finished the season with one of the highest save percentages in the league, helping steer Burnley to a remarkable seventh-place finish. Next season, Pope will be crucial for the Clarets as they aim for Europa League success.
Cardiff City - Aron Gunnarsson
Iceland star Gunnarsson was Cardiff's 2016/17 player of the season for his dependable performances in midfield. The 29-year-old is the longest-serving of Cardiff's newly-promoted squad and, as one of the few who have played in the top flight before, he will bring vital experience to the Bluebirds. He was hampered by injury last season, missing 34 games in total, but at his best he is the anchor of the team.
Chelsea - Ruben Loftus-Cheek
The 22-year-old's impressive form during his loan at Crystal Palace last season earned Loftus-Cheek a place in Gareth Southgate's World Cup squad. His graceful, long-legged strides are reminiscent of Michael Ballack, who played for Chelsea from 2006 until 2010. Until now, Loftus-Cheek has struggled for minutes in Chelsea's first team, but his speed and composure surely mark him as one to stay at Stamford Bridge.
Crystal Palace - Wilfried Zaha
The Ivory Coast forward enjoyed his most prolific campaign yet this season as he scored nine goals in 29 appearances, helping Palace recover from losing their first seven matches to finish 11th. Roy Hodgson's side failed to win any of the nine games Zaha missed. Last summer he signed a five-year deal worth around £110,000 a week, but Chelsea, Spurs, Liverpool and Manchester City have all shown interest. Zaha is the talisman who must inspire Palace as they look to progress into the top half of the table.
Everton - Jordan Pickford
England goalkeeper Pickford only joined the Toffees last summer from Sunderland, but he quickly established himself as one of the Merseyside club's key players. Playing behind a remarkably porous defence last term did little to help Pickford out, but he saved Everton's skins on many occasions. He has hit the headlines again this summer due to his performances for England at the World Cup, and Everton may find themselves fielding offers for Pickford before the transfer window closes. But, whatever they do, they cannot lose the 24-year-old glovesmna.
Fulham - Ryan Sessegnon
Fulham's 18-year-old starlet has been linked to Spurs, Manchester United and PSG and helped the Cottagers return to the Premier League with a 1-0 victory over Aston Villa in the Championship play-off final. He scored 16 times last season and created eight goals, earning him a place on the shortlist for the Professional Footballers Association's Young Player of the Year award - the first time in its 44-year history a player outside the top flight has been recognised.
Huddersfield - Aaron Mooy
Mooy shone in Australia's World Cup campaign even though they failed to get past the group stage. He joined the Terriers last season for £8million from Manchester City but has reportedly doubled in value as Everton and Southampton target the central midfielder. The 27-year-old was at the heart of David Wagner's team last season as he spearheaded attacks and defended dutifully. A dip in form earlier in the year has been ameliorated by his Socceroo performances - and Huddersfield fans will be hoping he brings that talent back to the north.
Leicester City - Ahmed Musa
Should Riyad Mahrez completed his expected move to Manchester City, Ahmed Musa has an opportunity to reignite his Leicester career. The attacker was in fine form at the World Cup, scoring both goals in Nigeria's 2-0 defeat of Iceland, yet he only scored four goals in his debut season at Leicester. Last season, he barely played before being shipped out to CSKA Moscow in January, where he duly scored seven goals in 16 appearances. The 25-year-old has proven he can perform on the world's biggest stage - so Leicester must give him another shot.
Liverpool - Loris Karius
Two catastrophic blunders in the Champions League final against Real Madrid may have reduced a legion of Liverpool fans and Karius himself to inconsolable tears, but the once-commanding Karius should not be banished into footballing wilderness just yet. At just 24, he has time to recover from an error-strewn season and the arrival of a new number one at Anfield could prove to be Karius's making. Without the pressure of being first in line, he can try to slowly regain Klopp and the fans' trust - and his damaged confidence.
Manchester City - John Stones
After injuries left him on the fringe at Manchester City in the second half of last season, Gareth Southgate's inclusion of Stones at the heart of his England squad proves the £47.5 million defender's true worth. The 24-year-old has played more minutes for England since November than he has for City in the league. A pragmatic defender, he works hard on the mental aspect of the game when his physique isn't enough to beat an attacker, and he asks teammates Kyle Walker and Vincent Kompany for help. When Kompany retires, Stones could be the man to fill his boots.
Manchester United - Luke Shaw
With just one year left on his contract at Old Trafford, defender Luke Shaw has limited time to prove his worth to Jose Mourinho. The trajectory of the 22-year-old's career has not gone as planned - the £30 million teenager has endured a horrific leg break, constant knocks and relentless public humiliation by Mourinho, yet remains optimistic about his chances. He has a lot to offer United, and it would be a great shame if they let Shaw, who is arguably still an exciting prospect, depart.
Newcastle - Aleksandar Mitrovic
The striker was superb in both attack and defence during Serbia's World Cup campaign, continuing the brilliant form he showed while on loan at Fulham in the second half of last season. Mitrovic's fantastic performances will certainly up the asking price should Benitez press on and sell him to Fulham this summer, but handing him a lifeline to resurrect his Toon career would be a far better investment.
Southampton - Ryan Bertrand
Two of Tottenham's key defenders, Danny Rose and Kieran Trippier, are in Gareth Southgate's England squad at the World Cup, so for them to show interest in the £30 million-rated left-back must be flattering. But Southampton's survival should be enough to keep Bertrand happy on the south coast for at least another season.
Spurs - Mousa Dembele
Belgium's Mousa Dembele has entered the final year of his Spurs contract, and the only confirmed detail of his future is that he will not join another English club amid interest from a host of sides throughout Europe. Concerns that the physical demands of the Premier League are getting too much for the 30-year-old must be acknowledged, but his commanding displayers in the heart of Tottenham's midfield suggest otherwise.
Watford - Nathaniel Chalobah
Chalobah's return to Watford last summer, on a permanent deal, was greeted with delight by Hornets supports. He started the season brilliantly, but then an injury suffered in September kept him out of action until the final day of the season. The midfielder will be like a new signing in 2018/19 now he is back to full fitness, and Chalobah is the player Watford's entire team should be built around.
West Ham United - Javier Hernandez
He might not have made the impact he wanted during his first season in London, but the Mexican striker now has 49 goals in 103 gaps, making him his country's all-time leading goalscorer. The 30-year-old has previously played for Manchester United and Bayer Leverkusen, and failed to have the desired effect under David Moyes. With Manuel Pellegrini now in charge, it's worth holding onto Chicharito for another season.
Wolves - Ruben Neves
The 21-year-old defensive midfielder has been linked with a move to Manchester United or Liverpool after being instrumental in Wolves' promotion from the Championship last season. He was the subject of a record £15.8million move from Porto last summer, but it is worth his while to bide his time before rushing back to a top European club. Neves himself appears to know this, having penned a new five-year contract with Wolves earlier this month.