"On his day he was a beast" – David Pocock picks his four toughest opponents

The 32-year-old, who retired from international rugby after 83 Tests following the 2019 World Cup last year, hung up his boots in 2020.

The Zimbabwe-born openside flanker, who made his debut for the Wallabies in 2008 and played at his first Rugby World Cup in 2011, was widely considered one of the best players in his position.

Pocock was appointed captain in 2012 to succeed an injured James Horwill but suffered the first of several serious knee injuries in 2013.

Pocock said: "Loved our tussles over the years. That one time he nailed me over here gets tweeted to me at least once a day. On his day he was a beast."

One of the most physical flankers in the game, he was dubbed a “threshing machine” by former Springboks coach Nick Mallett. Came back from injury and life-threatening illness to enjoy an immense international swansong at the 2015 World Cup. A carrying king who went on to join Saracens.

Pocock described the flanker as an 'irresistible force' that always brought the best out of him.

He led Wales to the 2011 World Cup semi-finals, winning 74 caps for his country as well as 49 as captain.

Playing in one British and Irish Lions tour is something rugby players aim for, but Warburton became their youngest ever captain for their 2013 tour of Australia, only for the side to lose the second Test after he sustained an injury.

Under his leadership, the Lions claimed a first Test series victory for 16 years when they beat Australia, and then drew the series against reigning world champions New Zealand in 2017.

David Pocock said: "He was such a big part of the psyche of the Welsh team and their guys really looked to him for direction. He was the go-to man for the Lions too." 

DID YOU KNOW? He was awarded an Honorary Fellowship by the University of South Wales in 2013

In a Q@A session on his Instagram page, the former Wallabies skipper simply posted a photo of Collins - who died in a car accident in France in 2015 along with his partner Alana Madill - in reply to the question "toughest opponent

Collins played 48 test matches for New Zealand between 2001 and 2007, and Super Rugby for the Hurricanes for a further year before heading to France.

DID YOU KNOW? He is considered to be one of hardest tacklers in rugby history, along with Brian Lima