James Haskell didn't hesitate when naming his toughest opponent from his career

The 2016 Six Nations Grand Slam winner was integral in England's first ever series win in Australia that same year.

But injuries since have seen his time at Test level suffer and the flanker in 2019 decided to call time on his playing days.

McCaw is a legendary New Zealand rugby union player, widely regarded as one of the greatest openside flankers of all time. Born on December 31, 1980, in Oamaru, New Zealand, McCaw's career spanned over a decade and a half, during which he became an icon of the sport.

He captained the New Zealand national team, the All Blacks, from 2006 until his retirement in 2015, leading them to numerous victories, including back-to-back Rugby World Cup titles in 2011 and 2015. Known for his exceptional leadership, tenacity, and unparalleled skills at the breakdown, McCaw's influence on the game remains profound even after his retirement.

Haskell said: "The thing that has stood out for me is his decision-making at the breakdown,  knowing when to compete for the ball, to clear out or to get back in the line, he always makes the right decision and he’s been doing it for years."

Burger is a South African rugby union player renowned for his ferocious playing style and immense physicality. Born on April 13, 1983, in Port Elizabeth, South Africa, Burger made a significant impact on the sport during his career.

Primarily playing as a flanker, he represented the South African national team, the Springboks, earning numerous caps and accolades. Burger's aggressive approach to the game, combined with his versatility and leadership qualities, made him a formidable presence on the field.

He played a pivotal role in South Africa's triumph at the 2007 Rugby World Cup and enjoyed success at both domestic and international levels throughout his illustrious career.

Haskell said: "A player who showed absolutely no regard for his body. He was just so incredibly physical and it was so tough playing against him."

Born on February 24, 1981, in Fogapoa, Samoa, Tuilagi made a significant impact in both international and club rugby. As a winger, he possessed remarkable strength and speed, making him a formidable opponent for any defense.

Tuilagi represented the Samoan national team, the Manu Samoa, earning numerous caps and showcasing his prowess on the global stage. He also enjoyed successful stints with various professional clubs, including Leicester Tigers in England's Premiership, where he became a fan favorite for his dynamic style of play.

Haskell said: "as pretty mortified when I found out he’s coming back to the Premiership with Newcastle a few years back. Just when you think you’re in the clear, the Tuilagis all start coming back. So, so powerful. I think he broke my ribs twice."

Wilkinson is an English rugby union legend, celebrated for his extraordinary skill, precision, and dedication to the sport. Born on May 25, 1979, in Frimley, England, Wilkinson's career is highlighted by his prowess as a fly-half and his iconic match-winning drop goal in the 2003 Rugby World Cup final, which secured England's victory over Australia.

Throughout his illustrious career, Wilkinson earned numerous accolades, including multiple Six Nations titles and domestic championships. Renowned for his relentless work ethic and commitment to perfection, he remains a revered figure in the world of rugby, inspiring generations with his passion and talent.

Wilkinson scored 1,246 during his 97 caps for England and the Lions. His finest hour, of course, came in 2003, when he slotted the drop goal that won the World Cup.

Haskell said: "Another who just constantly sets the standard. Close call with Dan Carter but I have to go for Jonny because of his attitude and the way he gives his all for the cause."

Born on February 13, 1974, in Fogapoa, Samoa, Tuilagi's career spanned over a decade, during which he left an indelible mark on the sport. Playing primarily as a powerful center or winger, he possessed exceptional strength and agility, often bulldozing through opposition defenses with ease.

Tuilagi represented the Samoan national team, showcasing his talents in various international tournaments. His intimidating presence on the field, coupled with his scoring ability and defensive prowess, made him a valuable asset to any team he played for, earning him admiration from fans and peers alike.

Haskell said: "There's no-one that's ever scared me because, I think, then you wouldn't play the game... but there was one player that I was super wary of and always wondered where he was. That was Henry Tuilagi.

"The problem with Henry is, for a start, he was about 135kgs. He used to stand in the back-field and people used to kick him the ball, and he would catch it and hold it in one hand. His hand was so big that it looked like a miniature rugby ball.

"And he would run... and just the f***ing hate in his face. He was just like whoop, whoop, whoop, whoop, and he would run so f***ing hard.

"Obviously the first person would be like, 'I'll do it [tackle him]!' and they'd just bounce off him... dust!

"Then I'd be like, 'I love you mum!', and dive into the spokes! It was horrific."