Goalkeepers are known as the last line of defence, because their mistakes almost always don't go unpunished. For this reason, most top teams across the continent feature reliable goalkeepers who can be counted on to produce the goods and keep the opposing team from scoring.It has been a trusted template for most successful teams in recent times. Last season, Real Madrid plotted their La Liga title triumph on the back of an uncharacteristic defensive resilience. Los Blancos conceded a league-low 25 goals thanks to the exploits of their Belgian goalkeeper Thibaut Courtois, who kept an impressive league-leading 18 clean sheets.In Italy, Samir Handanovic's exploits - 13 clean sheets - helped Inter Milan to a creditable second place last season, while this campaign, Gianluigi Donnarumma's brilliant form has played a key role in AC Milan topping the Serie A table.Serial Bundesliga winners Bayern Munich (13 goals conceded) may seem to be an anomaly in this regard, as the next five teams in the competition this season have all let in fewer goals. However, the Bavarian giants do have one of the world's best goalkeepers in Manuel Neuer.On that note, let us have a look at the ten goalkeepers with the most clean sheets in the 2020-21 season.10 goalkeepers with the most clean sheets in 2020-21 so farIn a surreal 2020-21 season, teams and players have had to endure one of the shortest-ever turnarounds in recent memory, as the previous season had a belated conclusion owing to the COVID-19 pandemic.Despite most big teams unsurprisingly struggling to get going in the new season, a few have taken rapid strides owing to the sublime form of their goalkeepers.Without further ado, let us have a look at the ten goalkeepers with the most clean sheets in all competitions in the ongoing season.#10 Koen Casteels (Wolfsburg) - 5 clean sheets in 10 gamesKoen CasteelsKoen Casteels has been a regular for Wolfsburg since the goalkeeper's arrival at the Bundesliga club in the summer of 2015.The 28-year-old Belgian custodian, who made his professional debut at Genk more than a decade ago, has kept 49 clean sheets in over 150 games in all competitions for Wolfsburg.Casteels has kept at least ten clean sheets in three of the last four seasons for his club. He has kept five clean sheets this season, three of them being in the Bundesliga and two apiece in Europa League qualifying and tournament proper.🇩🇪 Bundesliga Team of the Week pic.twitter.com/gdW3C1NROp— WhoScored.com (@WhoScored) November 23, 2020The Belgian international made the Bundesliga Team of the week last month for his fine form.#9 Ederson (Manchester City) - 6 clean sheets in 13 gamesEdersonBrazilian goalkeeper Ederson has a key player for Manchester City since his arrival under Pep Guardiola in the summer of 2017.The former Benfica custodian hit the ground running in his new surroundings, keeping 17 and 20 clean sheets respectively in consecutive seasons to help Manchester City win successive Premier League titles.📊| Ederson Stats: Ederson has kept 53 clean sheets in the Premier League since his debut in August 2017; 15 more than any other goalkeeper in this time.[Opta] pic.twitter.com/yXiiaPbU0F— City Chief (@City_Chief) October 17, 2020A rampaging Liverpool denied City a three-peat, but Ederson was a model of consistency in an otherwise disappointing season for City as the goalkeeper kept an impressive 17 clean sheets.Despite City enduring a troubled start to their domestic campaign this season, the Brazilian goalkeeper has kept three clean sheets in the Premier League. However, Ederson has been more impressive in the Champions League, where he has conceded only one goal in five games.#8 Roman Burki (Borussia Dortmund) - 6 clean sheets in 10 gamesRoman BurkiRoman Burki has been a standout performer for Borussia Dortmund since his arrival at the club in the summer of 2015.The 30-year-old Swiss goalkeeper, who has kept an impressive 82 clean sheets in all competitions in over 200 games for BVB, is generally regarded as one of the finest goalkeepers in the Bundesliga.The triple-save of dreams from Roman Bürki! 🧤Let's see what you've got @ZSCOfficial, @Palmeiras, @Trabzonspor, @NorwichCityFC, @CelticFC 👋#KeeperChallenge https://t.co/ZFOpRsy48a pic.twitter.com/LoI2C04LaH— Borussia Dortmund (@BlackYellow) April 23, 2020The exploits of Burki have been pivotal in BVB mounting a robust challenge to mighty Bayern Munich in the Bundesliga.The Swiss international has kept three clean sheets apiece in the Bundesliga (seven games) and Champions League (four games) this season.#7 Rui Silva (Granada) - 7 clean sheets in 16 gamesRui SilvaRui Silva kept 12 clean sheets in the La Liga last season to help Granada finish seventh in the league table and qualify for the Europa League.The 26-year-old, who is yet to debut for Portugal, has carried his good form into the 2020-21 season as well. Silva has kept three clean sheets in La Liga and has shut out the opposition in two games apiece in the Europa League qualifying and tournament proper.🔴⚪️ Granada's Rui Silva has kept 7 clean sheets in 13 games this season (all competitions) 👏@GranadaCdeF | #UEL pic.twitter.com/dtq3MAsCmP— UEFA Europa League (@EuropaLeague) November 11, 2020The former CD National goalkeeper has kept a decent 15 clean sheets in 45 La Liga games and has been key in Granada punching above their weight in the competition.