Diego Costa concedes he is afraid of what fitness coach Oscar Ortega has in store for him after arriving in Spain to complete his move to Atletico Madrid.
The LaLiga club confirmed on Thursday that they had agreed a transfer fee with Chelsea, reportedly in the region of EUR60million, to bring back the striker.
The 28-year-old landed in the capital on Friday and is due to undergo a medical and finalise personal terms with Diego Simeone's side in the coming days.
Costa has not played since last season's FA Cup final defeat to Arsenal, having spent the last two months in self-imposed exile in Brazil after being told by Blues boss Antonio Conte that he was not in his plans.
Although he insists he is in good shape, the Spain international expects to be given a gruelling training regime by Ortega as he attempts to regain optimal fitness ahead of a January comeback.
"I'm very happy to be back home," he told the media at Madrid's Barajas airport. "Everyone knew that I wanted to rejoin Atletico Madrid and I'm very grateful for the effort that [club chief executive officer] Miguel Angel Gil Marin has made.
"I'm in good shape physically. I'm not afraid about stepping back onto the scales; but I am afraid of 'Profe' Ortega's training sessions!
"I expect to give my all, as I have always done, and hopefully things will go well for me."