Oscar helped Chelsea draw a line beneath Juan Mata's departure with a fine free-kick in a 1-0 win over Stoke City in the FA Cup fourth round on Sunday.
Chelsea's Brazilian midfielder Oscar (R) celebrates scoring the opening goal with Chelsea's German striker Andre Schurrle (L) at Stamford Bridge in London on January 26, 2014
The Brazilian had dislodged Mata from his position as Chelsea's main playmaker, prompting the Spaniard to join Manchester United, and the quality of his goal demonstrated why manager Jose Mourinho rates him so highly.
The Blues failed to add to Oscar's first-half effort despite hitting the woodwork twice, although it was a largely comfortable victory, with Stoke rarely threatening to score an equaliser and force a replay.
Chelsea's reward is a mouthwatering fifth-round trip to Premier League rivals Manchester City.
"We are playing well and the team is confident," Mourinho told ITV.
"One-nil is short for the way we played and controlled the game. But the important thing was to win and not replay, because we don't need an extra match."
Stoke manager Mark Hughes said that Erik Pieters should not have been penalised for a challenge on Samuel Eto'o that yielded the free-kick from which Oscar scored, but he was encouraged by his side's display.
"Obviously it was a fantastic strike, but I didn't feel it was a free-kick," said the Welshman.
"We couldn't quite create enough clear openings. It was difficult for us, but I'm pleased with what we did. We stuck at it and didn't go under. I'd suggest there were more positives than negatives."
Mourinho opted to rest a number of senior players including John Terry and Petr Cech, but his decision to include Eto'o in his starting line-up raised eyebrows.
The forward scored a hat-trick in the 3-1 victory over Manchester United seven days previously, but the manager had been expected to rest Eto'o and hand Demba Ba a rare start.
However, Eto'o wasted little time justifying Mourinho's decision, quickly imposing himself on the Stoke back-line and drawing the foul that allowed Oscar to break the deadlock in spectacular style.
Eto'o's smart turn and shot in the second minute suggested this would be a long afternoon for Stoke, who were hoping to repeat their Premier League victory over the Blues in early December.
The visitors' initial response suggested otherwise, with Peter Crouch heading wide after getting ahead of his marker David Luiz three minutes later.
Stoke struggled to put Cech's replacement Mark Schwarzer under real pressure, but they matched Chelsea in the midfield areas for long periods.
Chelsea, though, looked capable of capitalising on any Stoke error and should have taken the lead from a breakaway after Marko Arnautovic gave the ball away carelessly inside the home half.
Then, when Pieters was penalised for a tackle from behind on Eto'o, Oscar produced a memorable free-kick that gave Mourinho's side a 27th-minute lead.
Stoke complained angrily that the decision to penalise Pieters was harsh and television replays suggested that they had a point.
Their sense of injustice was fuelled when Oscar lifted the free-kick over the wall and into the top-left corner, bending so much that it wrong-footed Stoke goalkeeper Asmir Begovic.
Having finally broken through Stoke's defence, Chelsea took control of the remainder of the first half, although Stephen Ireland did provide a scare when he fired a left-foot shot into the side-netting.
Oscar should have added a second goal when he broke into Begovic's area and beat the goalkeeper with a powerful shot that cannoned to safety off the upright.
And Chelsea maintained their momentum after the break when Andre Schurrle found himself in a similar position before firing against the crossbar.
Stoke offered little in return and could have been on the end of a more comprehensive defeat if Eto'o had not missed from close range late on, while Ramires had a penalty appeal turned down.