Timo Werner scored twice from the spot after taking over penalty duties and revealed Jorginho was “cool” with the decision.
Werner struck both penalties in the first half as Chelsea left themselves well placed to qualify for the knock-out stages as they also kept a fifth consecutive clean sheet.
Chelsea striker Werner has now got seven goals after Jorginho handed over penalty duties after missing his previous two spot kicks.
Werner said: “Before the game the manager said when there is a penalty I should take it. Two today is crazy, not all days.
"I take it and good goals for a striker but hopefully I can go on like this.
"I am happy, I am happy Jorginho is cool with it.
"It is another point that speaks for our team, we are not selfish. We all go in one direction;which is good.
"Now we want to win the Group.”
Chelsea boss Frank Lampard said: “I think we deserved it. It was a tough game. They were tough opposition and we won pretty well.”
Rennes boss Julien Stephan was unhappy Brazilian left back Dalbert was sent off before half time for a second yellow card after conceding a second penalty for handball.
Stephan said: “It was very frustrating because the players would have wanted to play in different conditions. I don’t know why he decided to give handball for this and to give a second yellow card for this kind of thing kills the game.”
Meanwhile, Chelsea confirmed before the game that Germany forward Kai Havertz has tested positive for coronavirus and will have to self isolate for 10 days.
Lampard added: “Kai is very disappointed because he just wants to play football. He tested on Monday in the UEFA testing.
"He had very mild symptoms and they escalated slightly today but he’s fine.”
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