The former Sunderland midfielder completed his £20 million switch yesterday.
Dad Brian told The Sun: "I have been Jordan's biggest critic over the years but the lad has done all the hard work and now look at his reward.
"He has given up so much. He never goes clubbing, is teetotal and, to be honest, doesn't even have any other interests other than football.
"I know he may have missed out on a lot of stuff his mates are getting up to.
"But I've said to him, 'You can start drinking when you're 35, just concentrate on your football'.
"He took up a bit of golf once but it just acted as a bit of relief from the training he did as a kid. From the age of seven he trained three times a week.
"And when he wasn't at the club he was in the back garden practising and practising.
"I remember when he was eight he turned round and said to me 'Dad, I'm going to be a professional footballer'.
"He had a brilliant determination and focus. I would just tell him to believe in himself."