Jose Mourinho largely refrained from hitting back at Antonio Conte over an unflattering remark about the Manchester United manager's most recent departure from Stamford Bridge, the boss of the Red Devils sufficing himself instead with what may have been a sly reference to the Italian's elaborately restored hairline. 

As Chelsea prepare to try and retain the crown they earned last term, Conte warned his players they will need to "avoid a Mourinho season", referring to the infamous 2015-16 campaign.

The Blues finished 10th under caretaker Guus Hiddink that term, Mourinho having been sacked before Christmas amid a succession of nightmare performances. 

Speaking after United's 3-0 friendly win over Valerenga on Sunday, the Portuguese was reluctant to return fire directly, although he did perhaps squeeze in a subtle acknowledgement of the efforts made by the previously follicly-challenged Juventus and Italy player. 

"I don't know," he said.

"I could answer in many different ways but I'm not going to lose my hair to speak about Antonio Conte."

United continued their largely impressive pre-season form, bouncing back from an International Champions Cup loss to Barcelona by winning thanks to goals from Marouane Fellaini, Romelu Lukaku and Scott McTominay.

With one more friendly – against Sampdoria on Wednesday – to come before the UEFA Super Cup clash against Real Madrid, Mourinho said he was happy with his team's preparations so far.

"It was good for us because of the good pitch, the opponent was very well organised, trying to play from the back," he said.

"After the U.S. and jet lag, it was a good match where I could play 45 minutes each player and now a little rest before the Sampdoria match.

"Until now, no injuries, so let's see if we can start the season in this positive situation."

United open their Premier League season at home to West Ham on August 13.