Costa replaced Chelsea winger Willian at the start of the second period and there was immediately a greater urgency from Brazil.
Still off the pace after recovering from a late-season club injury, Neymar compensated what he lacked in touch with unbridled emotion, as he repeatedly engaged in physical tussles, followed by remonstrations with the Costa Rican defenders in their Group E encounter in St. Petersburg on Friday.
Brazil's head coach Tite didn't escape the Twitter treatment either. While the initial reactions were focussed on the victory, later many people also highlighted the goal scored by Neymar and his emotional outburst on the field. "So I don't think this is true".
Not many people will agree with me however, for if there is one think that Brazil knows how to do it is to play at worldwide level, and they will not be letting their guard down throughout this match, which for reference is going to be the very first match played today. Costa Rica can no longer reach the last 16.
"I returned the ball because it was not this ball that was going to win us the game".
US Open to change seeding rules for tennis players returning after pregnancy
Because, to be honest, I feel pressure to be Serena. "It was this whole new strength that I actually never knew I had". Williams, made her return to the tour in March at Indian Wells and Miami, following the birth of her daughter.
Barcelona's Coutinho, who scored with a brilliant strike in the opening game, failed to find his range and Chelsea's Willian, taken off at half-time, was very bad on the right.
This led to Costa Rica being able to go on the counter-attack, but they too were unable to get past the Brazilian defence.
Both Firmino and Costa had come on as substitutes in the second half.
Facing their South American rivals in the second game, many questions were raised on how Brazil would approach this match-up, especially with the news that their superstar Neymar was not 100 per cent fit.
Then came the moment Neymar seemed to be impeded in the box - the decision will be debated, but thankfully for the referee, it did not decide the day. Tellingly, he didn't go on as a straight swap for fellow striker Gabriel Jesus but instead for central midfielder Paulinho.
Brazil beats Costa Rica in tense encounter
In the end, Brazil found the net with Philippe Coutinho prodding home a late victor through the legs of Keylor Navas . Brazil now need a draw in their final game against Serbia to ensure their passage through to the knockout stages.
Musa, Nigeria's all-time leading World Cup scorer with four goals, has played well against Argentina before.
While plenty of fans spotted what Marcelo was up to, he wasn't even booked - though many pointed out his actions were just as bad as what Sergi Roberto did to him during El Clasico back in May, with the Barcelona man receiving a red card.
Switzerland maestro Xherdan Shaqiri completed his team's comeback against Serbia by rounding off a breakaway with a slick finish in the last minute in Kaliningrad.
Aleksandar Mitrovic scored for Serbia with a header in the fifth minute. Tears of "joy, of overcoming, of willpower and desire to win" that show how desperate he is to succeed at the finals this summer. Musa deftly controlled the ball before slamming it past Iceland goalkeeper Hannes Halldorsson on the half-volley.
Iceland had a chance to get one back but Gylfi Sigurdsson sent a penalty kick way over the Nigeria bar in the 83rd minute.
Mohamed Salah considering retiring from Egypt duty over controversy with Ramzan Kadyrov
That has been followed by Kadyrov granting honorary citizenship to Salah at a banquet on Friday night, as reported by Sky Sports. He returned for Egypt's 3-1 loss against the hosts but was not at his sharpest despite scoring a penalty.
"It's unusual that we are still in the race", said Iceland coach Heimir Hallgrimsson.