Ray Lewis has made a career out of causing people pain. Through 16 remarkable seasons in the NFL, he has recorded 2,004 tackles. But numbers are only half the story. If Lewis has become one of the greatest defensive players ever to grace the sport, it is in significant part because of what Sports Illustrated's SL Price described as the "palpable promise of violence" that accompanies his presence on a football field.

Such is the ferocity of Lewis's game that in the past even some of his Baltimore Ravens team-mates have admitted to harbouring concerns for their welfare when playing alongside him, due to the risk that they might accidentally get in his way. Lewis himself, however, professes to using pain – whether physical or emotional – as his greatest motivational tool.

Addressing a group of teenagers during a visit to South London earlier this summer, Lewis candidly explained how he took a serious interest in exercise only after seeing his mother subjected to domestic abuse by a then boyfriend. The oldest of five siblings, with his father having walked out for good when Ray was just six, he took it upon himself to become the family's protector.

"I'd shuffle a deck of cards, turn over the top five and add the numbers up," said Lewis. "That's how many push-ups I would do that day. Jacks were 15, queens 20, kings 25. Aces were 50."

As he grew stronger he began to excel at football and wrestling. Enrolled at the high school his father – also a talented sportsman – had attended, Lewis made a point of breaking every one of his father's school records. But even that could not provide him with closure. Two decades, one Super Bowl victory and multiple NFL records later, Lewis is still driven, in part, by the same demons.

"I never forget it. And if you never forget it, then your motivation never stops," Lewis tells the Guardian when asked what keeps him coming back, after 16 years in one of the more punishing positions in such a brutally physical sport. "Some people take certain things and they try to forget what that pain felt like. I don't. I take that same pain and I chase it every time I walk in a weight room. Any time I feel like I don't want to get up or whatever, it just clicks in."

'Pain is a Gift from God'

It is a message that confronts any visitor to Lewis's house, where there hangs a picture bearing the message "Pain is a Gift from God". Religion, too, plays a big part in Lewis's life these days – popping up in almost every answer he gives during our interview. He has been known to preach the Christian Gospel at his church on the Sundays – when he is not busy distributing God's gift to NFL running backs.

Even the darkest period of Lewis's adult life is perceived by him as just another step in a divine plan. Only Lewis, along with the handful of others present, truly knows what happened outside Atlanta's Cobalt Lounge nightclub on 31 January 2000, but the court case which followed is familiar even to many with no interest in his sport.

Then just 24 but already making waves in the league, Lewis was not involved in Super Bowl XXXIV but he had flown into town to enjoy the festivities. In the small hours of the morning after the game, he was with a group that became involved in a fight which started outside the club and finished with two young men – Jacinth Baker and Richard Lollar – stabbed to death. Lewis, along with two others, would subsequently be charged with murder.

The charge was soon dropped – Lewis instead receiving 12 months' probation and a $250,000 league fine after pleading guilty only to obstruction of justice. But in the court of public opinion, not everyone was convinced. Certain fans of opposing teams, in particular, would remind him many times over the next few seasons that they believed he should be behind bars.

Twelve years on, Lewis might not have won everyone over but he has succeeded in greatly rehabilitating his public image – in part through his prodigious charity work, geared heavily towards creating support networks for kids in disadvantaged areas. His visit to London, which was paid for out of his own pocket, was prompted by a letter from an amateur team, the Warriors, who are seeking to use the sport as a tool to keep young men from tough neighbourhoods out of gangs.

"If I hadn't gone through that [the murder accusation], I wouldn't be speaking to you today," says Lewis. "It's the only reason that God used me to go through it. Because he knew that I would never turn my back on him. Now he receives all the glory, because he was able to expose who I was as a person, through a tragedy.

"Now everybody who meets me says, 'Oh, you're nothing like I thought you was.' Well you never met me! But when people meet me, they meet what my mother raised, which was a hell of a man, by herself. And that's my honour, that's what my goal is, to always keep my mum's name ringing, because I know what sacrifices she went through for me."

If it is hard not to wonder how the victims' families would feel about the deaths being cast as part of a holy plan to glorify Lewis, then it is also only fair to note that he prefaces any discussion of Atlanta by stressing that his only hesitation in revisiting the topic stems from a desire not to cause any further hurt.

"People who wasn't involved in it has no sympathy for the people who was affected," he says. "A lot of people was affected."

It cannot have been easy for those same families to watch Lewis be crowned as a Super Bowl champion just one year later – the screaming, swaggering, shimmying leader of a record-breaking Baltimore defence. An intentionally intimidating on-field persona played into the hands of those seeking to portray him as a violent brute, yet in person he comes across as anything but – genial, optimistic and never far removed from the broadest of grins.

Becoming somebody else on gameday is, to Lewis's mind, just part of the job. As he neatly puts it: "You got to play the game pissed off."

He would know – having become arguably the greatest middle linebacker ever. The first player ever to combine 40 sacks and 30 interceptions over the course of a career, Lewis has been named to the league's all-star game, the Pro Bowl, 13 times in 16 years. His longevity is extraordinary. Now 37, he is not as fast as he used to be but he still led the Ravens in tackles last season, despite missing four games.

'Seau was my hero'

Asked to name the best linebacker of all time, Ray Lewis names Junior Seau. Photograph: Stephen Dunn/Reuters

Asked who he considers the best linebacker of all time, Lewis's first thought is Junior Seau – the former San Diego Charger, Miami Dolphin and New England Patriot who took his own life earlier this year, at the age of just 43.

"Seau was my hero," says Lewis. "His was the first jersey I ever had.

"But outside of him, LT. [Former New York Giants linebacker] Lawrence [Taylor] played the game the way the game was supposed to be played. Lawrence changed the way the game was played. Any time you can change a game, you can make people adjust their whole game plan, then you have to be considered number one or even zero."

There was speculation throughout 2011 that Lewis was preparing to retire, that it would be his final season. But after the Ravens' gut-wrenching defeat to New England in the AFC Championship game – Billy Cundiff missing a short field goal that would have tied the scores with 15 seconds remaining, moments after his team-mate Lee Evans had let a game-winning touchdown pass slip through his grasp – Lewis confirmed that he would be back.

He insists now that his decision to return was not affected by the outcome of that game.

"Not really, because by the time I won the Super Bowl years ago – I had enough money then," he says. "If we won it last year, I know I would still have brothers that would look at me and say 'let's go back again'. You've got something left in the tank, so why give it up?

"I'm a prideful person when it comes to competition. If I'm in practice, and someone's beating me in practice, and then I get in the game and someone's beating me in the game, consistently, then I've got to look at myself and say, 'OK, what's going on? You not loving it any more, or what?' I'll know when I'm done. But I just can't tell you, straight up, when that would ever be."

'I would never play nowhere else'

One thing he does know, is that he would never play for anyone other than Baltimore – the team who drafted him in 1996 and a city which has taken him to their hearts.

"No way. Never, I would never play nowhere else," he says. "That city… You know, sometimes when God crowns you with a city, it's bigger than any championship. And that city is in love with me as much as I'm in love with it. My purpose was there."

Nor does he harbour any ill-feelings towards the players whose mistakes cost the Ravens so dearly on that final drive in New England. During an emotional post-game speech that day, he commanded his team-mates not to be dispirited, and he remains resolutely on message.

"I never blamed Billy Cundiff," he replies when asked if the kicker – who was cut by the Ravens this week – has been forgiven. "Or Lee Evans for dropping the pass. One play has never won or lost a game, ever. And there's no man that's ever walked this earth that's perfect. Take Michael Jordan – on the board of the million shots that he made that people remember, I remember the ones that he didn't. The ones that lost that last second game. And I was like 'damn', but he was all right with it."

It is clear that Jordan has been another of Lewis's inspirations. During his speech in London, Lewis commands his audience to go out and read the basketball player's story – to note how greatness was not bestowed but earned through simple, unending, hard work.

"Stop taking all these breaks," he implores. "Stop acting like this one's going to fall in your lap."

Back in our conversation, he argues that Cundiff ought to be lauded, not vilified.

"It takes a brave soldier to take that shot. And he'll tell you that I told him that. Because as great as they say I am as a football player, if they asked me to do that kick, I've got to say no. Because that ain't what I do. So you could never put anything like that on one person."

Looking forward, he states his belief that the Ravens are well-equipped to put that disappointment behind them this year with another run at the championship.

"We're stronger," he says. "Every year we've been making a run at the playoffs, and people don't really understand how young we are. [Starting quarterback] Joe Flacco and [running back] Ray Rice are young. [Wide receiver] Torrey Smith was a rookie last year."

He neglects to mention the middle linebacker, Ray Lewis: 37 years young.