Jose Mourinho delivered a damning assessment of Ruben Loftus-Cheek's performance during the post-season friendly win over Sydney FC.
The Blues ran out comfortable 1-0 winners following Loic Remy's stunning first-half opener in front of a capacity crowd Down Under.
But it was Mourinho's dim view of the display put in by one of his club's most promising rising stars that has made the headlines.
Speaking after the game, Mourinho piled into the 19-year-old suggesting his attitude was "unacceptable".
"When Chelsea had the ball he was playing very well, but when Sydney had the ball I think he was more impressed by watching Nemanja Matic and John Obi Mikel work, instead of him working.
"So, with Ruben, it's one step back in terms of my relationship with him. If he doesn't know what it is to play for me and Chelsea, it's one step back.
"He has to learn that at 19 you have to run three times more than the others, you have to play to your limits and not play like a superstar with the ball at your feet because this is not Under-18s.
"The Under-18 competition is too easy for him. He's too good to play in the Under-18s.
In pictures: Chelsea sign off for the season by winning Down Under.
Loftus-Cheek came on for Diego Costa after 41 minutes but after appearing to struggle with a back injury was hooked off again just after the break.
"I don't accept that when he's playing in midfield with Mikel and Matic, when we don't have the ball he doesn't press, doesn't have intensity and he's waiting for everybody else to recover the ball.
"I don't accept that in the superstars so how can I accept that in a kid? He has to learn what it takes to play for us."
"He said it was a pain in his back but to me it looked like he only had that pain when Sydney had the ball."
Mourinho confirmed earlier this year that Loftus-Cheek, a star of the club's academy, would play a much more significant role next season.