Starsport report that Costa has been ordered back to London by the club, having failed to report for pre-season duty following the Confederations Cup.
A source close to Costa said: "I really don’t think he is in the right state of mind."
Rumours have been circulating all summer that Costa's relationship with his manager Antonio Conte has broken down and the mood of everyone won't be helped by Saturday's shock home defeat to Burnley.
The Blues have already signed Alvaro Morata this summer but Conte remains unconvinced by Michy Batshuayi so with Costa still away, he would like to bolster his strike force.
Belotti began his senior career by helping to fire Palermo to promotion in 2014 and has enjoyed two successful seasons at Torino. Having scored 12 goals in his first season at the club, Belotti scored 28 goals in 38 games in all competitions last season. Only Edin Dzeko for Roma and Dries Mertens for Napoli would score more than them in Italy.
Torino though are desperate to try and keep hold of their star player as they chase European football this season following a 9th place finish last term. Their valuation is £80m and aren't expected to listen to offers much lower than that figure. Other targets for Chelsea before the transfer window closes include Chelsea midfielder Danny Drinkwater and Arsenal's Alex Oxlade-Chamberlain.
Despite demanding Costa, who has insisted he only wants to play for Atletico Madrid, returns to training Chelsea are prepared for a stalemate with the Spain striker.