The result in Naples could prove to be of great importance for Rosenior whose appointment in place of Enzo Maresca was hardly greeted with open arms.
Rosenior’s lack of elite experience – having moved from sister club Strasbourg after stints with Derby County and Hull City in the Championship – saw him labelled by some as a ‘yes man’.
He also experienced the wrath of the fans who voiced anti-ownership chants questioning the ambition of the BlueCo.
Rosenior has been adamant from the start that his reply must be through results.
And he has put together an impressive set of results in his first weeks with five wins in six matches and the latest over a former Chelsea favourite should win him the confidence of more supporters.
“These players lost a manager that they really respected for reasons that are beyond my control or knowledge,” Rosenior told TNT Sports.
“So when you go through that as a young group, to accept a new manager the way they have done and for them to work as hard as they have done is a credit to them.
“It’s not about me or my ego or trying to prove anything. I’m trying to do the very best I can with my group, with my staff and hopefully we can have more and more really good nights like this.”
Rosenior’s introduction of Cole Palmer at half-time provided assisted both of Joao Pedro’s goals while Trevoh Chalobah added defensive solidity after coming on later in the half as the Blues restricted Napoli to a single shot on target after the break.
The Chelsea manager added: “I’m learning all the time about my team, about what we’re capable of.
“I really wanted to be front-footed today. I wanted to go out and win the game.”
His impetus was rewarded with a win that helps Chelsea avoid adding a two-legged play-off to their already busy schedule.
“It’s massive – that is huge for us to be able to be able to work with the players on the training round,” Rosenior said.
Bigger challenges await Rosenior and his young squad as they enter the business end of the competition but the London-born coach is optimistic.
“You have to enjoy this job,” he said.
“We’re the luckiest people in the world to do this job. You have to enjoy these moments, but we want more.
“You’re in the Champions League, so at the end of the day you have to play against the best and beat the best.”