Costa scored 20 times in Chelsea's 2016-17 Premier League title-winning campaign, but the 28-year-old is said to have had a strained relationship with Blues boss Antonio Conte in the second half of the season.
Last month, Costa revealed that Conte had told him to leave Stamford Bridge this summer, and the striker has been strongly linked with a return to Atletico, despite the Spanish club's transfer ban.
The video, which can be seen below, allegedly shows Costa, who is clearly in the colours of his former club, telling teammate Cesc Fabregas to 'give a hug to Conte' as the pair's relationship hits a new low.
INCLUSO HASTA SE ATREVE A DECIR UN AUPA ATLETI EN EL SEGUNDO 15. VA CIEGUÍSIMO. DIEGO C DESECANDENADO. MI DELANTERO. pic.twitter.com/LJsrlwU33M— ANNOUNCE DIEGO COSTA (@RauIgarcismo) July 16, 2017
Costa, who was strongly linked with a move to the Chinese Super League earlier this year, has scored 58 times in 120 games for Chelsea, landing two Premier League titles in the process.