"His departure annoys me because his performances haven't been accompanied by goals in a team that doesn't wait".
Atletico Madrid manager Diego Simeone has expressed his frustrations with the club's decision to sell Argentine striker Luciano Vietto.
A frustrating summer for the 29-year-old followed, with a return to Atletico agreed while the La Liga giants were working under the restrictions of a transfer ban.
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Atletico tried several times to find a replacement for Costa.
Antoine Griezmann completed the rout with a goal from a free kick in stoppage time, moments after the home side had defender Marc Trilles sent off for a second yellow card.
"We must remain relaxed, as extremes are bad", he said.
Vietto is yet to score in 10 games for Atletico this season.
The additions of Costa and Vitolo may mean Atletico will look to move one or more of its forwards.
The fact he was told via text only added insult to injury and it made Costa's exit from Chelsea all the more messy. His spot on Spain's World Cup squad is in jeopardy after he was dropped by coach Julen Lopetegui given his hiatus from football. "I am ready to give it my all and later the coach will decide".