By Chelsea correspondent Tony Hughes| Premier League expert with experience of breaking big stories, including exclusives like this

Eden Hazard has returned to full training for Chelsea as he targets a return in Sunday’s Premier League showdown against Arsenal, Football Insider sources understand.

But the Belgian’s team-mate Diego Costa is struggling to be available for the landmark fixture at Emirates Stadium.

A Chelsea source has told Football Insider that Hazard trained with the first-team squad on Wednesday for the first time since injuring his groin against Crystal Palace on 3 January.

Manager Guus Hiddink, who urged Hazard to prove his fitness in training this week after missing the team’s last three matches, will now consider the reigning Footballer of the Year for the London derby.

Speaking about Hazard last Friday, Hiddink said: “We have to be a little bit careful that we don’t fall again with a setback,” Hiddink explained.”

“From Tuesday to Thursday he must have intense training sessions. Then we’ll decide if he can join us in the Arsenal game next weekend.”

Costa is rated a serious doubt for Sunday’s match after suffering a shin injury Chelsea’s 3-3 Premier League thriller with Everton last weekend.

Diego Costa has returned to form since Guus Hiddink was appointed manager

Fitness race: Costa is struggling with a shin injury ahead of Arsenal match

Although the results have showed there is only bruising to his tibia, and crucially no break or fracture, Costa has not yet trained this week.

Against Everton, the Spain international scored a goal and supplied an assist as Chelsea fought back from 2-0 down before limping off at the 80-minute mark with the score at 2-2.

He has scored five goals in five games under Hiddink and the Blues boss cannot afford to lose the striker to a lengthy spell on the sidelines.

Meanwhile, as reported by Football Insider, Chelsea are working on a deal to sign Corinthians striker Alexandre Pato.