The Chelsea duo transformed since Mourinho's exit...and one player who continues to struggle

New year, new Chelsea? Guus Hiddink's side produced arguably their most impressive performance of the season in a 3-0 victory over Crystal Palace at Selhurst Park.

Palace have proven difficult to beat so far this season and, prior to the loss on Sunday, only Tottenham could boast a better defensive record.

But in a display far removed from their struggles under Jose Mourinho, Chelsea played with a confidence and verve to to their game to pick up what was only their second win away from home in the Premier League and against a team in the top 10.

Mourinho suggested his players had 'betrayed' him shortly before he was sacked by Roman Abramovich and the numbers suggested several players had underperformed dramatically compared to their title-winning season.

And, under new boss Hiddink and since Mourinho's exit, two Chelsea players look transformed...

Diego Costa's performances since Mourinho's departure have been much more in tune with expectations of the striker.

Back from suspension against Crystal Palace, Costa showed strength, a burst of pace and composure to latch on to a Cesc Fabregas pass before playing in Oscar for Chelsea to open the scoring.

Costa then arrived in the right place at the right time to scramble in a low pass from close range to wrap up the victory for Hiddink's side.

The tap-in at Selhurst Park was Costa's third goal in as many games since Hiddink arrived at the club, following his double against Watford.

That tally over the last three games represents as many as he had managed in 16 outings under Mourinho this season.

Oscar helped to kickstart the post-Mourinho era with a penalty in a 3-1 win over Sunderland, before Hiddink was officially appointed.

And while the Brazilian missed from the spot to deny Hiddink a first victory back at Stamford Bridge against Watford, his performances have been notably improved.

The playmaker pulled the strings against Palace from the start and opened the scoring with a simple finish after good work by Costa.

Oscar linked up well with Costa and Fabregas throughout the game and also provided a somewhat fortuitous assist for Willian, who blasted home from long range after his compatriot had been brought down mid-dribble.

In the last four games, Oscar has passed the ball more on average than he did under Mourinho in 10 outings and boasts a better pass accuracy percentage. He is also attempting more shots and dribbles under Hiddink.

But it wasn't all plain sailing. Eden Hazard was forced off after just 15 minutes with a groin problem having appeared to injure himself whilst taking a shot early on.

It has been a difficult start to the season for the PFA Player of the Year, who earned plaudits for his performance as false nine in the goalless draw against Manchester United but has largely been ineffectual this season.