John Obi Mikel's father has admitted he is worried by his son's behaviour.
The 19-year-old midfielder secured a £16 million switch to Chelsea from Lyn Oslo in the summer, but has yet to make his mark in The Premiership.
He has not played since being sent off against Reading last month, when his furious reaction to the dismissal earned him a warning from the Football Association.
Mikel has also infuriated manager Jose Mourinho with his casual attitude, and father Michael Obi has voiced his concern about what the future could hold if things do not change.
"We are very sad and his mother is worried. We have tried to get hold of him, but he no longer picks up our calls," he explained.
"I don't know why he is behaving like this and we are not happy about it. We are all involved in his football career, the whole family is worried and we hope to see a better Mikel."
However, Mikel's father insists his son is still held in high regard by Mourinho, and is hopeful that things will soon get back on track.
"I hope to see him return to action and I hope to see him play a good-boy role again, because his coach loves him," he said.
"Mourinho has shown more interest in him than in any other player in the team. As a young man, I expected him to concentrate on his career."