The ever-sceptical Jose Mourinho clearly has not learned any lessons from his fall-out with Samuel Eto'o over the striker's age last season.
Mourinho was caught on camera in February saying: "I have Eto'o but he is 32 years old, maybe 35, who knows?"
That prompted Eto'o's unforgettable old-man celebration a fortnight later as he mocked his manager after scoring Chelsea's opener in their 4-0 demolition of Tottenham.
But far from steering clear of the subject, Mourinho has now cast doubt on the age of one of his youngest stars, telling 19-year-old Kurt Zouma that he would have to rely on the results of a blood test to prove his age.
"In the squad, they have a bit of laugh at me, about my age," Zouma revealed. "Because I'm a big, solid guy of 19.
"Even the coach once, he made fun of me. There was a blood test, and he told me jokingly: 'Now we'll see if you've lied about your age'."
But while Mourinho's cynicism might have put Eto'o's nose (or should that be hip?) out of joint, Zouma appears to have taken the joke more lightly.
"Honestly, they're cool, they are open," the defender said.