Diego Costa joins Atletico Mineiro as a free agent after his contract ended with Diego Simeone's Atletico Madrid last June.
Frank Lampard's side dominated from start to finish thanks to an influential display from Hakim Ziyech.
Luis Suarez partnered Diego Costa for the first time and scored as Atletico Madrid beat struggling Celta Vigo 2-0 in La Liga on Saturday.
Diego Costa scored his first goal since October but Atletico Madrid missed the chance to move into La Liga's top four by drawing 1-1 away at Athletic Bilbao.
Diego Costa was accused of failing to declare payments totalling over 5.15 million euros from his move to Chelsea in 2014.
Atletico Madrid's comfortable win puts them above Real Madrid in the La Liga table and level on points with Barcelona.
Diego Costa has agreed to pay 1.7 million euros to Spain's tax agency which was investigating him for non-payment of taxes on image rights.
Diego Costa had a hat-trick by halftime and added one more goal before he was sent off in the 63rd minute.
Diego Costa was sent off in the first half of Atletico's 2-0 defeat to Barcelona on Saturday for directing a crude insult towards referee Gil Manzano.
Costa sustained a thigh strain while playing for Atletico Madrid against Club Brugge in the Champions League on Wednesday.