Morata made an explosive start to his Stamford Bridge career, scoring six goals in six league appearances at the start of 2017-18, but things quickly soured for the Spain international.

A mysterious back problem blighted much of the campaign and he only scored a further five goals in the top flight and four in cup competitions.
Morata has shown encouraging signs of a return to form since Maurizio Sarri replaced Conte as head coach

Morata described how he played part of last season while taking painkilling injections he received from a doctor in Germany, with his form suffering as a result.

"In today's world, it's normal that these [critical] things are said," he added. "Chelsea made a huge effort for me and it wasn't returned. I should have repaid them double. A player they pay for can't finish the season with 15 goals.

"People think we're machines. If I had stopped for three months, I would have come back with a clear head, but I was professional and I wanted to give everything.

"If I could go back, I would stop for two months. I was in pain, I went to Germany to see the doctor, paying for private planes. People believe the false life of Instagram what it shows you; they thought I was at home with my wife. Someday, I'll write a book about what I've been through."

source: http://m.goal.com/x/en/news/8/main/2018/09/05/47555162/morata-contes-tactics-made-me-suffer-at-chelsea