Ireland U19 defender Mark O'Brien has signed a four-year deal with Derby County
The 18-year-old Dublin born international has seized his chance in the first team this season, featuring in all seven Rams games.
O'Brien has started six matches at centre-half, starting in place of the injured Shaun Barker in five of the club's six Championship matches.
Manager Nigel Clough told the club website: "He has been playing well and deserves his contract."
O'Brien, who will now stay at Pride Park until the summer of 2015, had to undergo heart surgery in Novemer 2009.
And Clough has been impressed with how he has come back: "He has had to overcome some challenging hurdles but his attitude has been exemplary.
"He has taken his chance because of the injuries.
"He has shown to everybody he is an honest, brave and committed player who will put his head where some players would not even put their feet."
The new deal is the latest chapter in O'Brien's remarkable story.
Only months after making his first-team debut for Derby as a 16-year-old at Watford on the final day of the 2008-9 season, O'Brien was told he needed heart surgery.
He had the operation in October 2009 and was back in action for the Academy six months later.
His progress was hindered towards the end of last season when he underwent surgery on his ankle and then injuries to a number of the club's centre-backs opened the first-team door for him.
But he is not taking anything for granted.
"I feel I am still easing my way in because anything can happen," said O'Brien.
"Shaun Barker, Russell Anderson and Jake Buxton can come straight back in for me, so I cannot think I have got my feet under the first-team table or anything like that.
"My aspirations are the same as they were at the start of the season. I wanted to be a part of the squad and get some games under my belt. That has not changed.
"Hopefully I can keep progressing.
"All I can do is try to keep playing and doing as well as I can."
O'Brien's first League start came in the 1-0 win at Watford last month and he also helped the team to keep clean sheets in the victories over Blackpool and Doncaster Rovers.
Clough has been delighted with the youngster's attitude.
"It has been exemplary when you think what he has gone through for such a young person, never mind a young footballer," said Clough.
"To come through and get in the side, everybody is delighted for him. He is back on the pitch, he is healthy and he is playing well.
"He deserves his deal.
"He is ahead of schedule and it is out of necessity he is in the team.
"When you look at the centre-halves on our books, certainly they are more experienced than Mark but he has come in and taken his chance.
"Until such time as somebody is fit who we think is better than him and can do a better job, he will stay in the team."
