The Spanish striker, left on the bench for the Premier League champions' win over Watford on Monday night, was spotted nipping out for a mid-match snack during the game.
Asked about Costa's extra-curricular activity afterwards manager Antonio Conte saw the funny side.
Indeed he only wished the 28-year-old had taken the time to bring him some food too.
"Which type of food did he have?," he asked the assembled journalists at his post-match press conference. "It is important, this... chocolate cake? In this case I am very angry with him.
"He must think to give me a bit of chocolate cake to share. I was suffering during the game. To eat a bit of cake or chocolate, that would be good.
"Next time I will tell him to think of me as well and share."
Costa was an unused substitute as the Blues eventually saw off the Hornets, Cesc Fabregas climbing off the bench to grab a late winner.Reuse content