In truth, Chelsea‘s 5-1 win flattered them on Saturday, but substitutes Liam Delap, Pedro Neto, Enzo Fernandez and Estevao Willian proved too much for a tired Charlton side to cope with.
Rosenior is the first Chelsea manager to win his opening game since Antonio Conte in August 2016, enjoying the biggest winning margin since Luiz Felipe Scolari in August 2008.
“I have to say I was delighted with the starting XI,” Rosenior said. “I was delighted with the front three. I felt Ale [Garnacho] kept going in his one-v-ones.
“Marc Guiu was magnificent, deserved his goal. Jamie [Gittens] looked like he was going at the defenders. He looked like he could create in a lot of moments. So a lot of real positives and a good start.”
The most impressive performer was defender Jorrel Hato, who scored the opening goal and playing in a role filled by Marc Cucurella last season.
Hato, 19, made inverted runs into attacking midfield positions when Chelsea were on the front foot, found himself in dangerous areas and ultimately capitalised.
The £37m summer signing from Ajax has previously struggled at Stamford Bridge, but since Maresca left the club, he has produced arguably his three best performances, playing significant minutes against Manchester City and Fulham in recent league matches.
“I saw him play at Fulham,” Rosenior said. “I was so impressed with him then. He’s taken that form on to another level today. Not just in terms of his goal – I felt his defensive attributes were top.”
There was concern when Rosenior explained Cole Palmer, Reece James and Malo Gusto were left out because of to knocks sustained in defeat at Fulham last Wednesday – particularly with tougher tests to come.
Arsenal are next in the Carabao Cup semi-final on Wednesday, while Chelsea welcome Brentford to Stamford Bridge on Saturday.
“He is going to be judged on how he does against decent teams in the Champions League, against Arsenal, Manchester City, Liverpool, Aston Villa – those are the teams he will be judged against, so we will have to see,” former Chelsea winger Pat Nevin told 5 Live.
“He has got a great month with a lot of games where he can see a lot of players. Four home league games, two away league games – and one of them is Wolves, who haven’t had a great season so far.
“There’s no easy route, but this is as friendly as it could be. He will have learned which of his players are fringe players. There are quite a few he will be pleased with.”
It wasn’t all happiness, though: Chelsea supporters continued their protest against the ownership throughout the match and even chanted “attack, attack, attack” as their team waited until the brink of half-time for the breakthrough.
The atmosphere among fans remains febrile amid distrust of the ownership. It is a potential pitfall for Rosenior to be wary of given that, as a recruit from Todd Boehly and Clearlake Capital’s other club Strasbourg, he could easily be labelled a yes-man.
When asked about the chants, Rosenior said: “All I’m going to focus on at the moment is working as hard as I possibly can to help this team achieve the potential – the unlimited potential – that it has. And if you concentrate and focus on your work, hopefully people will see that we’re onto a good thing.”