Despite the COVID-19 pandemic wrecking clubs' finances, teams that wish to contend in multiple competitions have not hesitated to bring in quality players.
Manchester City recently landed Jack Grealish on a big transfer and are close to signing striker Harry Kane. Manchester United have brought in Jadon Sancho and Raphael Varane; Chelsea have acquired Romelu Lukaku.
Elsewhere in Europe, Bayern Munich have landed exciting young centre-back Dayot Upamecano; Atletico Madrid have signed Copa America 2021 winner Rodrigo de Paul; AS Roma have acquired the services of Tammy Abraham. Ligue 1 giants PSG have made a spate of high-profile transfers to lay down a gauntlet for the rest of the continent.
Nevertheless, there are a few players who are so integral to their team's cause that they are considered virtually undroppable. That's because their absence tends to significantly affect their team's balance and efficacy. On that note, here's a look at ten such players:
#10 N'Golo Kante
N'Golo Kante's stock has been on the rise after he played a stellar role in Leicester City's improbable triumph in the 2015-16 Premier League.
Chelsea immediately snapped up the defensive midfielder, who has won a Premier League, Champions League, Europa League, FA Cup and UEFA Super Cup in six seasons at the club. The Blues have had a few managerial changes since Kante's arrival, but the Frenchman is usually one of the first names on Chelsea's team sheet.
The 30-year-old, regarded as one of the finest defensive midfielders in the game at the moment, has also excelled for France, winning the 2018 FIFA World Cup with Les Bleus. He was one of Chelsea's standout performers in last season's Champions League final against Manchester City.
Kante has made over 200 appearances for Chelsea, scoring 11 goals and providing ten assists. But it's his assured presence in the middle of the park, breaking up opponents' plays and starting moves from the back that makes Kante a key player for both club and country.
#9 Bruno Fernandes
Bruno Fernandes has been like a breath of fresh air since his arrival at Old Trafford in January 2020. In one and a half seasons at the club, the 26-year-old has already racked up 43 goals in 81 games, with 29 of these strikes coming in the Premier League.
Fernandes, who is the club's designated penalty taker and is also a set-piece specialist, opened his account in the 2021-22 Premier League by scoring his first hat-trick for Manchester United.
The Portuguese, who had a dismal campaign with Portugal at Euro 2020, has seemingly rediscovered his mojo, which augurs well for his club's hopes of winning their first league title in almost a decade.
#8 Harry Kane
Harry Kane has been a standout performer for club and country over the years. Last season, the English striker enjoyed one of his career-best campaigns, topping both goalscorers and assist charts with 23 goals and 14 assists.
Despite his exploits, Kane endured another trophyless campaign as Tottenham Hotspur failed to qualify for the Champions League or Europa League after leading the league early on.
The Englishman, who scored four times in England's run to the Euro 2020 final, has racked up an impressive 221 strikes for Spurs. The 28-year-old missed his team's season-opening win against holders Manchester City, whom he is likely to join in the next few days.
However, it remains to be seen if City will be able to meet Spurs' valuation of the English international before the transfer window closes.
#7 Karim Benzema
Karim Benzema is one of the last big names left in the La Liga after the departures of Sergio Ramos and Lionel Messi.
During a more than decade-long stint in the Spanish capital, the 33-year-old has been a standout performer for Real Madrid, despite spending nine years largely under the shadow of his former teammate Cristiano Ronaldo.
The Frenchman, who scored on his return to the international fold at Euro 2020, opened his campaign for the 2021-22 season with a brace in Madrid's 4-1 win away at Alaves.
Benzema has scored an impressive 281 times in over 550 appearances for Madrid, winning three La Liga and four Champions League titles. Despite turning 33, Benzema is expected to play a key role as Carlo Ancelotti's men seek to win their second La Liga title in three years.
#6 Kevin De Bruyne
Kevin De Bruyne is arguably the best midfielder in the game at the moment. The Manchester City and Belgium midfield metronome has produced consistently impressive performances for club and country.
The 30-year-old is the crown jewel in Pep Guardiola's expensively assembled Manchester City team. The assist king has racked up a century of assists across competitions for the Sky Blues, and has played a key role in their three Premier League wins in the last four years.
De Bruyne has also been a star performer for Belgium as well, scoring once and assisting twice in the Red Devils' campaign at Euro 2020, which ended in the quarter-finals against eventual champions Italy.
#5 Erling Haaland
Erling Haaland is one of the most exciting young strikers in the game at the moment.
After bursting onto the Champions League stage with a hat-trick on debut, Haaland has gone from strength to strength since moving to Borussia Dortmund in January last year.
The 21-year-old, who is the subject of interest from a bevy of top clubs across the continent, has scored an impressive 62 times in as many games for the Bundesliga giants. Haaland opened his account for the season with a sumptuous brace on Matchday 1, in a game where he also provided three assists as Dortmund beat Eintracht Frankfurt 5-2.
Considering his staggering exploits - Haaland scored 41 goals in all competitions last season - the Norwegian is unlikely to remain at Dortmund for too long, though.
#4 Virgil van Dijk
Virgil van Dijk has been a key player for Liverpool since arriving at the club more than three years ago.
The Dutchman, widely regarded as one of the finest centre-backs in the game, has been one of the key players in Jurgen Klopp's team. He did not miss a league game for Liverpool in successive campaigns, as the Reds pushed Manchester City all the way in 2018-19 before winning their first league title in three decades a year later.
However, in the Anfield derby against Everton last season, van Dijk suffered a season-ending injury. In van Dijk's absence, Liverpool's title defence spectacularly imploded, before the club recovered to finish third.
The Dutchman returned to action in Liverpool's 3-0 win over Norwich City in their 2021-22 Premier League season opener, after a nine-month layoff.
Virgil van Dijk, one of the first names in Jurgen Klopp's XI, immediately made his presence felt at the heart of the Liverpool defense, helping the Reds kickstart their campaign for a second league title in three years with a resounding victory.
#3 Robert Lewandowski
Robert Lewandowski is the most prolific striker in the game at the moment, scoring goals galore for club and country.
The 2021-22 season is barely a few days old, but Lewandowski has already scored thrice in two games to move to within three goals of reaching the 300-goal mark for Bayern Munich.
Lewandowski, who has scored in each of his last 14 games for the Bundesliga giants, broke the late Gerd Muller's fifty-year-old record of most goals (40) in a Bundesliga season last campaign. The prolific Pole, in the process, bagged his first European Golden Show award.
The 32-year-old striker also dazzled at Euro 2020, scoring thrice, even as Poland finished bottom of their group to crash out of the tournament.
Under Julian Nagelsmann, Lewandowski, who won the continental treble in 2019-20, will be one of the key players in Bayern Munich's bid to win a record-extending tenth consecutive Bundesliga title.
#2 Cristiano Ronaldo
Cristiano Ronaldo is arguably one of the finest players to have graced the game. The Portuguese has scored goals and won titles galore during an illustrious near two-decade-long career for club and country.
Despite turning 36 earlier this year, Ronaldo became the first player in Juventus history to score 100 goals in their first three seasons at the club. It was a shame that despite Ronaldo (29 goals) winning his first Capocannonieri award, Juventus failed to win the Serie A title for the first time in ten years.
After a prolific campaign at Euro 2020, where he scored five goals and assisted once, Ronaldo will look to hit the ground running when the 2021-22 Serie A season commences this weekend.
Under the return of Massimiliano Allegri, the Bianconeri will once again turn to Ronaldo for goals as they seek a return to league-winning ways.
#1 Lionel Messi
Lionel Messi is one of the greatest one-club players in the history of the game. During a 17-season-long stint at Barcelona, Messi registered almost 1100 goal contributions (672 goals, 305 assists), winning two continental trebles, six Ballon d'Ors and eight Pichichi awards.
However, after Barcelona failed to renew his contract this summer owing to La Liga's financial fair play rules, Messi was snapped up by Ligue 1 giants PSG on a free transfer.
Messi is yet to debut for his new club, but when he does, his attacking partnership with Kylian Mbappe and Neymar is expected to help PSG conquer Europe for the first time and also reassert their domestic dominance.
Under compatriot Mauricio Pochettino, Messi will look to hit the ground running in a rather less competitive league and continue his staggering exploits in the Champions League.