Of all the hundreds of millions of pounds pumped into the club by Russian owner Roman Abramovich, the seven million paid to Rennes for Cech have arguably offered the greatest return.
When Cech kept a clean sheet on his debut in 2004 – a 1-0 win over Manchester United – it was a portent of things to come.
Later that season, as Chelsea marched to their first English title for 50 years under Jose Mourinho, the Czech Republic keeper set a then Premier League record of 1,025 minutes without conceding a goal.
He kept 21 clean sheets in all that season and 100 in the Premier League in his first 180 games.
On Saturday, when Chelsea eased past Hull City 2-0 to go top of the Premier League, he was at it again, taking his tally of shutouts to a club record 209, edging past Peter Bonetti.
It was also his 150th Premier League clean sheet and, at the relatively young age of 31 for a keeper, Cech is surely heading towards a top flight record.
His calm authority often goes unnoticed but Mourinho, looking to mark his return to the club with the league title, knows the importance of the Czech stopper.
“In 2004 he arrived and we had at that time a fantastic goalkeeper Carlo Cudicini and Petr had Carlo behind him for these couple of years 2004-06 and he coped with that pressure.
“Now as a mature man and after so many years at the same club he sets a new record and normally one more season and he has to beat the Premier League record,” Mourinho said of Cech, who has played 457 times for the club compared to the 729 Bonetti played between 1959-79.
Cech, who has lifted the league title three times with Chelsea and also won the 2012 Champions League, had one of his easier afternoons at Hull but said the result was vital as Chelsea ramp up the pressure at the top.
“We want to win the league if we can and hopefully clean sheets will help us achieve our targets,” he said.
“Now we’re top of the league for the first time in a long time and hopefully we can stay there.
“We hope to keep going. We are getting better and today was a very difficult game. But we were very solid and good in attack and that’s why we score goals.”
Cech is now just 20 behind the Premier League record of 170 clean sheets currently held by former Liverpool, West Ham United, Aston Villa, Manchester City and Portsmouth keeper David James.
(Reporting by Martyn Herman; editing by Clare Lovell)