Over the years, many fine players have performed consistently for some of the biggest clubs in the world.
Although the term 'big' is a subjective one, it generally refers to one of the top clubs in Europe's top-five leagues. Clubs from the Premier League, La Liga, Serie A, Bundesliga and Ligue 1 - not necessarily in that order - often do well in the biggest of competitions.
While most top clubs do not necessarily depend on one player for success, there have been a few players who pick themselves in their teams' starting lineups. And their absence tends to adversely impact their teams' performances.
On that note, here's a look at the most important player at each of the ten biggest clubs, in no particular order, in the continent:
#10 Sergio Busquets - Barcelona
After the departure of club talisman Lionel Messi this summer, Sergio Busquets has become one of the key players for Barcelona.
One of the most famous La Masia graduates of this century, Busquets proved his worth under Pep Guardiola, and hasn't looked back since. The 33-year-old doesn't tally too many goal contributions, as he often does the 'dirty' work in the center of the park.
However, the Barcelona captain, an eight-time La Liga winner, had one of his better campaigns in the league last season, registering five assists.
With three league games under his belt this season, Spain's Euro 2020 captain (632) is approaching the 650-game mark for Barcelona.
#9 Jan Oblak - Atletico Madrid
Jan Oblak has been a standout player for Atletico Madrid since his arrival at the club in the summer of 2014.
The 28-year-old custodian kept a league-high 18 clean sheets last season to help the Rojiblancos win their first La Liga title in seven years. Such is his importance to the Atletico cause that Oblak has missed only two league games in the last four seasons, and none in the last two.
The Slovenian international has kept an impressive 160 clean sheets in 307 appearances across competitions for Atletico. Oblak is a five-time Zamora Trophy winner - awarded to the goalkeeper who keeps the most clean sheets in a league season.
#8 Leonardo Bonucci - Juventus
Leonardo Bonucci has been a key player for Juventus for well over a decade. The 34-year-old is one of the premier goalscoring centre-backs in the Italian top flight.
Bonucci, an eight-time Serie A winner with the Bianconeri, has scored multiple league goals for the club in each of his last seven seasons. Suffice to say, the Italy international is a formidable presence at both ends of the field.
The veteran centre-back recently made news by becoming the oldest scorer in a European Championship final. Bonucci also scored in the subsequent penalty shootout as Italy beat England to win their second Euro title.
Bonucci is only five games away from playing his 450th game for the club, a milestone he should reach by the end of the year.
#7 Virgil Van Dijk - Liverpool
Virgil Van Dijk is one of the best centre-backs in the game at the moment. Since arriving at Liverpool in January 2018, the Dutchman has been a colossal presence in their rearguard.
He did not miss a single league game in his next two full seasons as Liverpool won their first-ever Premier League title in 2019-20. Van Dijk has also helped the Reds to successive Champions League finals (2018 and 2019), with Liverpool winning the second one.
Van Dijk rarely gets dribbled past and makes his presence felt at the other end of the pitch too. After suffering a season-ending injury last season, Van Dijk is back to his usual best this campaign. He has played four league games this season, helping Liverpool to a four-way tie at the top.
In his absence last season, holders Liverpool endured a wretched campaign before recovering to finish third.