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There are a number of players who joined Chelsea following Roman Abramovich's takeover and went on to play a huge part in their subsequent success, but perhaps none were as important as Petr Cech's arrival in 2004.
Signed by Claudio Ranieri, by the time Cech actually joined Chelsea Jose Mourinho was in charge and the Czech Republic international quickly usurped Carlo Cudicini as the club's number one, helping the Blues to their first league title in 50 years during his debut campaign.
That year included a Premier League record run of 1,025 minutes without conceding a goal, which has since been surpassed, as Chelsea let in just 15 goals all season - still the fewest in a single Premier League campaign.
Cech went on to win four Premier League titles, four FA Cups, three League Cups, the Champions League and the Europa League during his time at Stamford Bridge, eventually leaving for Arsenal in 2015 having made 494 appearances for Chelsea - enough to put him sixth on the all-time list.
Cech kept a club-record 220 clean sheets in that time and currently holds the record for most clean sheets in Premier League history, winning the division's Golden Gloves on three occasions during his Stamford Bridge career.
Voted Chelsea's Player of the Year in 2010-11, Cech was also twice included in the PFA Team of the Year and has been named Europe's best goalkeeper three times.