The 27-year-old ex-Bayern Munich winger is coming into his own at his new club as the Italian club look to keep their bid for titles burning on three fronts.
Juventus, who have a game in hand, are just one point behind Napoli in the Serie A title race and are also through to their fourth consecutive Coppa Italia final, and Costa’s skills have helped them along the way.
Massimiliano Allegri’s side next head to Wembley Stadium for Wednesday’s Champions League last 16 second-leg tie against Tottenham Hotspur with the tie finely balanced at 2-2.
Juventus, who won the title in 1985 and 1996, have been runners-up in Europe’s elite competition twice in the past three editions.
This year’s quest remains in the balance after Allegri’s side threw away a two-goal lead earned by Gonzalo Higuaín’s double in the opening nine minutes of the first leg in Turin last month.
Allegri has heaped praise on Costa, who has in recent months provided game-changing speed down the wing and been a thorn in the side of opposition defences.
“Costa was excellent at both ends of the pitch,” said Allegri after the Brazilian’s performance in inflicting a first defeat of the season on Napoli in December.
The Brazilian again shone in the Coppa Italia semifinal against Atalanta last month as Juventus booked a place in the final against AC Milan.
“Costa put himself behind the centre-forward, and that broke the game open,” said Allegri.
Costa moved to Turin initially on loan with an option to buy him from Bayern Munich in a club-record 46 million euro (RM222 million) deal for the German club last summer, in what was seen as a last-gasp bid to revive his career for the World Cup in Russia. He has scored three goals and made six assists in 31 appearances for Juventus.
He has stepped up during a tricky period for the champions’ with injuries to top players including Federico Bernardeschi, Higuaín, and Paulo Dybala.
Higuaín remains in doubt for London because of a persistent left ankle pain, but Dybala has returned and scored the winner against Lazio at the weekend as part of a three-pronged attack which included Costa and Alex Sandro.
“I’m improving with the team and the time I set for myself in Italian football which has been something new to me,” said Costa. “I’ve grown tactically and technically.”
Costa joined Bayern from Ukrainian club Shakhtar Donetsk for 30 million euros (RM145 million) in 2015, but despite helping them win two Bundesliga titles, he fell down the pecking order under Carlo Ancelotti.
He started his career at Brazilian club Grêmio between 2008 and 2010 before moving to the Ukrainian club, where he won the domestic treble in 2011.
He recently admitted helping to throw a football game playing as a teenager for Grêmio to influence the outcome of the Brazilian title.
Club bosses and thousands of fans had implored the team to throw the match against Flamengo in 2009, according to Costa, as victory would have seen their hated rivals Internacional secure the title.
“If we’d beaten Flamengo, we could have died. The Gremio fans would have killed us,” he said.
To avoid that, Costa said he spent the second half dribbling the ball away from the goal. Flamengo ran out easy winners and “everyone was happy.”
Capped 22 times with three goals for Brazil, Costa has also worked his way back after his international career had stalled by persistent injuries.
He was called up for friendlies against England and Japan last November and is growing in confidence to earn a spot in Brazil coach Tite’s squad for Russia.