Andre Schurrle
Reports suggest Jose Mourinho is demanding more from World Cup winner Andre SchurrleGetty

Chelsea boss Jose Mourinho has told Andre Schurrle he must bulk up if he is to consistently challenge for a spot in his first team, reports suggest.

World Cup winner Schurrle has seen his opportunities limited this season having started five Premier League games for the Blues this term.

The 24-year-old told IBTimes UK in December a mystery illness has contributed to his poor form but he remained a peripheral figure over the festive period despite the frantic fixture list.

Despite starting three of the club's opening four games of the season, his role in the side has rapidly declined. In his last two appearances for Chelsea, against Southampton on 28 December and in the FA Cup third-round victory over Watford on Sunday 4 January, Mourinho opted to haul the German international off at half-time.

While the Chelsea boss insisted afterwards that he was unconcerned by the player's wavering form, Schurrle's future at Stamford Bridge has remained under scrutiny.

The Times and Bild now suggest Mourinho has ordered the player to work on improving his physical attributes in order to boost his chances of grasping a first-team opportunity. The forward has reportedly been handed a "bespoke training programme" and told to concentrate on increasing his muscle mass.

Schurrle arrived at Stamford Bridge in the summer of 2013 following a £18m move from Bayer Leverkusen. After an impressive debut season in English football, his inconsistent form this term has seen him linked with a winter move away from the club.

But Mourinho has remained adamant he will not make major changes to his first-team squad, insisting the likes of Schurrle, Mohamed Salah and Petr Cech will not be sold under any circumstances.