Spain striker Costa agreed a move back to Atletico from Premier League champions Chelsea in September but was unable to play for Diego Simeone’s side until the new year due to the club’s transfer ban.
The 29-year-old, who spent four years at Stamford Bridge before falling out with boss Antonio Conte last summer, quickly made up for lost time as he grabbed Atletico’s third goal of the evening just five minutes after coming off the bench to replace Angel Correa in the 65th minute.
It helped wrap up a routine win for Atletico in the first leg of their last-16 clash with the Spanish third division side after defender Diego Godin and Costa’s fellow former Chelsea striker Fernando Torres gave them a two-goal half-time lead.
France forward Antoine Griezmann completed the scoring in stoppage time following the late dismissal of Lleida defender Marc Trilles.
Elsewhere, two goals from Bosnia-Herzegovina forward Ermedin Demirovic helped last season’s runners-up Alaves secure a 3-1 success at Formentera.
Meanwhile, Barcelona boss Ernesto Valverde has admitted his admiration of Philippe Coutinho but refused to be drawn on reports of a fresh bid for the Liverpool star.
LaLiga leaders Barca are expected to make a January move for the talented Brazilian having seen a series of offers rejected last summer.
While Valverde admitted the 25-year-old is a quality player, he preferred to speak about players already tied to the Catalan club.
“He plays on another team, he’s a good player and we do not know what will happen in the future, the ones that worry me most are the ones I have right now,” said Valverde ahead of tonight’s Copa del Rey match against Celta Vigo.
When asked again about Coutinho, Valverde replied: “I have nothing to say about Coutinho, we respect that he is in another club.”
Earlier, former Liverpool defender Jamie Carragher urged the club not to sell Coutinho in the current transfer window but agree a deal for him to leave this summer.
Carragher tweeted: “Best thing @LFC is agree the BIG fee for Coutinho to go in the summer like we’ve done with (Naby) Keita, not now.
“What do the club gain by doing it now? Top 4 & CL progression seriously risked if they sell in Jan, & difficult to replace him now. If he goes on strike he damages himself.”
Coutinho missed the start of the season with a back problem but has been in outstanding form, scoring seven goals in his last eight games.
Barcelona’s record signing Ousmane Dembele could return from a four-month injury lay-off against Celta Vigo this evening, but Valverde will be without star forwards Lionel Messi and Luis Suarez.
France international Dembele, bought from Borussia Dortmund for an initial fee of around €110m during the summer, injured a hamstring in just his third appearance for Barca and has been sidelined since mid-September.
Valverde has named the 20-year-old forward in his squad to face Celta in the first leg of the last 16, although Messi and Suarez will not travel to the Balaidos after recently returning from Christmas breaks in South America.
Valverde said: “Recovering Ousmane is very positive for us.”
“(Messi and Suarez) arrived back Tuesday because they are further away from their families (in South America).
“I do not intend to risk anything with any injury.”