A 5ft 10in (1.79m) attacking midfielder who can also play wide, he has a reputation for good pass-and-move football, protecting the ball and choosing the right moment to play passes.
He made his debut on the opening day of the 2012/13 Premier League season, coming on as a second-half substitute despite having trained just twice with his team-mates, and displayed a previously lesser known turn of pace to add to his sharp passing game.
Oscar made his first start for the club in the Champions League draw against Juventus at Stamford Bridge, announcing his arrival in style with two strikes in the space of a couple of minutes, the second of which will live long in the memory, and since then has become a regular starter for Roberto Di Matteo's side.
His fondness for goals of the spectacular variety continued in the home game against Shakhtar Donetsk when he produced a stunning effort to score from 35 yards.
Having come through the youth system at Sao Paulo, he graduated to the first team in 2008, the same year he was part of the Brazil side that won the Under-17 World Championships. That feat had also been achieved the previous year.
His time at Sao Paulo came to an end in December 2010 with a move to Internacional, a club based in Porto Alegre in the very south of the country. In 2011 and 2012 they won the local state championship and Internacional also used Oscar as a substitute in the 2010 FIFA Club World Cup, the competition to be contested by Chelsea in December, although they suffered a shock defeat by Congolese side Mazembe.
Oscar, who played international football at every level from Under-15 to Under-20, made his debut for Brazil's senior side in September 2011, coming on as a substitute in a 0-0 draw against big rivals Argentina.
He made his full debut in a win over Denmark in May he scored his first international goal in June 2012, although Brazil were beaten 4-3 by Argentina in New Jersey, USA, as Lionel Messi scored a hat-trick.
Oscar's most notable moment on the international stage so far was in the final of the Under 20 World Cup in Colombia when he scored a hat-trick in a 3-2 extra-time win against Portugal.
He also played a pivotal role as Brazil clinched a silver medal at the London 2012 Olympics.