From Roy Keane's temper to Wayne Rooney's wild tackles, former goalkeeper Roy Carroll says Manchester United's old-school training sessions demonstrated the winning mentality at the club.
Carroll spent four years at Old Trafford and went on to win a Premier League medal in 2002-03, and also lift the FA Cup.
The ex-Northern Ireland international played his part in a dominant reign under legendary former manager Sir Alex Ferguson, and no-nonsense captain Keane.
Carroll says both men were driven to succeed, and their hunger to win was ever-present - even during simple 5-a-side games.
He also recalls a young striker by the name of Rooney flying into 'knee-high' tackles during box drills.
"I worked with so many great players, and they were all different," Carroll told Belfast Live's That's What I Call Football podcast.
"You had Paul Scholes who turned up for training, did the boxes and kicked a few balls into the net. He is a family man, so he went home after training.
"You then had Cristiano Ronaldo who was a different character. He worked so hard on his game as you would imagine, staying after sessions to practice.
"It was scary how many of these young players came through the ranks at the time. I remember Rooney coming in and he was so young.
"We did these boxes. You had six or seven players outside and two players in the middle. And Rooney was just slide tackling people when he was in the middle.
"He was going for the knees and everything. And it was just the speed of the passing and the ball, it was unbelievable. It was proper boxes.
"We try and tell the young lads now with Northern Ireland: Do it quicker. Do it faster. We have been there and know what it is like, and you want those lads to take it on board."
And Carroll says nobody hated losing more than inspirational skipper Keane, even if was just a training session.
"Roy Keane. Jesus, I have never seen a man like it," Carroll said.
"In the 5-a-side, I used to be scared of playing for him in case I let a goal in. Because he would knock me out.
"But that was the winning mentality at Manchester United. You lose a 5-a-side game in training, everyone was upset.
"If we conceded a goal on Saturday, we would go up the other end and score two or three. It was like a basketball game.
"It was the mentality of 'we're going to win no matter what'. And that was the mentality of Sir Alex Ferguson."
While Manchester United's players were elevated to football stars following their rise to the top under Ferguson, Carroll says there were no heirs or graces about the all-conquering squad.
Carroll arrived from Wigan Athletic in 2001 after being watched by Ferguson for two years.
He admits he "didn't sleep for two weeks" ahead of his arrival at Old Trafford, but says "superstars" like David Beckham helped make the daunting transition a lot easier.
"I was really nervous at the first training session. But then David Beckham comes up and introduces himself, and I just stared at him and replied, 'I know who you are'. I didn't even introduce myself," Carroll laughed.
"I watched these superstars on TV, but when I arrived they weren't superstars. They were so welcoming, every single one of them.
"That made me feel better. Some clubs in the lower leagues, the players hardly speak to you when you arrive.
"When I went through League Two and Three, it was a lot harder moving clubs. But when I moved to the Premier League, everyone at Manchester United made me feel welcome.
"And my first game was against Aston Villa in the sixth game of the season and I loved it."
Former Northern Ireland shot-stopper Carroll, who won 45 caps for his country, recalls having to earn his stripes when he first burst onto the international scene as a teenager.
"When I first came in to the Northern Ireland squad at 18 years old there was big Taggs (Gerry Taggart), Neil Lennon, Jim Magilton. I remember sitting at the front of the bus because you weren't allowed to sit at back for three or four years," he said.
"It is a bit more comfortable now for young players coming into the squad.
READ NEXT:
Jack O'Donoghue says Munster have learned to 'cop on' if Saints come on heavy
Tributes pour in after death of young GAA star Saoirse Buckley
Latest Burnley bid for Michael Obafemi turned down by Swansea City
Aidan O'Shea breaks silence over Lee Keegan retirement after South Africa holiday
Get the latest sports headlines straight to your inbox by signing up for free email alerts
