The Spaniard, who moved to Old Trafford from Atletico Madrid in 2011, also struggled to stick to the correct diet.
"He'd eat too many tacos," Steele told United We Stand fanzine. "We had him in the gym a lot. He hated it. They don't do the gym in Spain as much.
"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 has now secured his place as first-choice goalkeeper with the Premier League champions.