David De Gea "trained poorly" and ate "too many tacos" when he arrived at Manchester United, according to his former goalkeeping coach at Old Trafford.
The Spaniard arrived at Manchester United in 2011 from Atletico Madrid in a deal reportedly worth around £18 million, but initially struggled to settle in the Premier League and came in for criticism for his erratic performances.
He was briefly dropped for understudy Anders Lindegaard last season but has since established himself as the Red Devils' number one.
Now former Manchester United goalkeeping coach Eric Steele, who helped De Gea improve after his rocky start, has revealed the 22-year-old's struggles early on were, at least in part, down to his own attitude.
"His first six months were horrendous," he said in an interview with Manchester United fanzine United We Stand. "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."
Steele left Old Trafford over this summer following the retirement of Sir Alex Ferguson and the arrival of David Moyes.
"He could be very solemn in training, he was always better in a group. Solemn because he was tired, mentally and physically," he continued.
"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."
Despite De Gea's early struggles, Steele now feels as though the young shotstopper is finding his feet and settling into life in England, although he admits his former student isn't quite the finished article just yet.
Steele says De Gea possesses: "Calmness, composure and inner strength. Nothing fazes him. Playing in front of 76,000? No problem. Very few possess that."
He added the goalkeeper, who was voted into the PFA team of the year last season, is "well liked" and is "part of the Hispanic set with their own sense of humour."
However he warned: "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."