David de Gea's struggles adapting to life in England are laid bare in a revealing interview that offers a rare insight into the problems the Manchester United goalkeeper has encountered and the frustrations he caused their coaching staff.

Eric Steele, the goalkeeping coach widely credited with De Gea's improvement, talks about a goalkeeper who is "lazy" when it comes to learning English and initially had a habit of "training poorly", as well as eating "too many tacos". Asked whether the player is now more settled in Manchester, after intermittent rumours of him wanting to return to Spain, Steele says the 22-year-old understands he is at a good club but there are "still issues".

Steele left Old Trafford after David Moyes's appointment in the summer, having been instrumental in De Gea's development since Sir Alex Ferguson signed him from Atlético Madrid for £17.8m two years earlier. His pride is apparent as he talks of the Spaniard's transformation into the goalkeeper voted on to the Professional Footballers' Association team of the year last season. "Calmness, composure and inner strength. Nothing fazes him. Playing in front of 76,000? No problem. Very few possess that."

Yet Steele, an almost paternal figure for De Gea, openly admits the goalkeeper has had considerable issues at Old Trafford. "His first six months were horrendous," he says. "One issue with him was that he was just 71 kilos. We worked with him on and off the field to make him more powerful. We changed his lifestyle. He would finish training and want to go home. When I told him to come back in the afternoon he'd ask: 'Why?'

"There were lifestyle issues. He'd sleep two or three times a day. He'd have his main meal late at night. He'd eat too many tacos. We pushed protein drinks on him straight after training. We physically made him drink. We had him in the gym a lot. He hated it. They don't do the gym in Spain as much. We needed to build his core strength."

De Gea, according to Steele, could "be very solemn in training, he was always better in a group. Solemn because he was tired, mentally and physically. I told him he needed to train better, that he was on show every day. There were times in his first season when he trained poorly. I told him that players made decisions for managers, not the other way around. That he should be first, not last out for training."

Steele goes to explain why he started taking Spanish lessons rather than relying on De Gea to improve his English. "We needed to be able to communicate with each other straight away, even if it was just the basic terms. David is lazy in his desire to learn English. So I learned. I kept telling him to work on his English."

De Gea, he says, is "well-liked" at Old Trafford, a "part of the Hispanic set with their own sense of humour", and is still taking English lessons. He identifies the turning point as a save against Juan Mata during a 3-3 draw at Stamford Bridge, seven months into his first season, and there is praise for Ferguson for persevering with him. "Fans criticised him [De Gea]. The media, too. But the manager stuck by him and protected him in the media. He knew he had a long-term asset. He was only 19 and that was a risk, but the manager had been to watch him with me and knew how good he was."

De Gea has subsequently been linked with a return to Spain amid rumours of homesickness. "I heard the speculation," Steele tells the latest edition of United We Stand fanzine, published before the 2-1 defeat against West Brom. "I told him not to get sidetracked, that if he did well at United then he'd have a great career. I said: 'Who would you go back to? One of the big two. Would you want to go to Real, rivals of Atlético?' No. It would have to be Barcelona, but he sees that United has been good for him. He captained Spain Under-21s in the summer off the back of his United form. He's going to be with the seniors now in a country with the best goalkeepers in the world."

To the question ofwhether De Gea is more settled now, Steele replies: "Yes, but there are still issues. He's living in a huge house with his mum and dad. He's got a beautiful girlfriend who lives in Barcelona. We pushed him to move on his own. Living with your parents helps and hinders."