James rifled a fine goal into the roof of the net as Chelsea overwhelmed AC Milan 3-0 at Stamford Bridge on Wednesday to put their Champions League campaign back on track.
The 22-year-old also laid on Pierre-Emerick Aubameyang's goal in another show of strength, dominating the right flank in his already customary fashion.
Chalobah impressed too, amid Chelsea's morale-boosting win and clean sheet, in replacing Wesley Fofana, who was left to sweat on a worrying knee injury.
England star James continues to flex his potent talent, leaving his fellow Chelsea academy graduate Chalobah seeing no need to hold back any praise.
"We are lucky to have him," said Chalobah.
"He is an unbelievable player who can do all sides of the game. He can defend, get us goals and get us assists.
"It's a pleasure to play with him.
"He's definitely one of the best in the world, I've said it from day one. And, right now, he could be the best in the world."
Summer recruit Fofana will sweat on the results of scans after suffering a potentially serious knee injury.
The £69.5million defender hobbled out of the action in the first half, having earlier opened the scoring with a calm finish.
Fofana left Stamford Bridge on crutches and with his right knee in a brace, as much underlining the potential severity of any injury as for precaution.
Chelsea will hope the 21-year-old has avoided a long-term problem, but boss Graham Potter admitted his concern after the Blues' win over last term's Serie A champions.
Chalobah's fine substitute showing against Milan was his first Chelsea appearance since the 2-1 Premier League win over Leicester in August, and just his second outing of the season.
The Blues centre-back ignored outside interest in the summer window to stay and fight for chances at Chelsea, and revealed he is grafting hard to impress new manager Potter.
Chelsea leapfrogged Milan in Group E to revive their hopes of knock-out stage qualification, and a win at the San Siro on Tuesday would leave the Blues in charge of their chances of progression.
"For me I am at Chelsea, this is my club; every time I get the chance, I want to show the manager that I am good enough to play," said Chalobah.
"Any chance I get I need to do my best and let the manager decide.
"It starts in training and we've been working behind the scenes a lot on things people don't see.
"We are building a solid team and the manager wants us to have that connection and I think we had that against Milan.
"It was a good game. To come into a game like that, I had to be ready and I've been ready for the past however many weeks it has been.
"I was ready and I thought I did a job and helped the team get three points.
"It was an important three points for us. We didn't start the group as well as we wanted to and it was a good reaction."