If you're squeamish, look away now.
In this week's Flash Back Friday picture special, we're remembering some of the worst and most tackles and fouls ever seen on a football pitch.
Leg-breaking lunges, two-footed tackles, stamps, kung-fu kicks and flying elbows - this one definitely isn't for the faint-hearted.
Many of the challenges illustrated below resulted in red cards - and rightly so - but others were only deemed worthy of a caution. Astonishing!
As these https://cdn.standardmedia.co.ke/images prove, sometimes the beautiful game gets ugly...
Nigel de Jong on Xabi Alonso Spain vs Netherlands, World Cup Final, 2010
"It was one of the worst tackles I have ever suffered," said Alonso after De Jong's kung-fu kick to the chest in the 2010 World Cup Final between Spain and the Netherlands.
Graeme Souness on Gheorghe Rotariu Rangers vs Steaua Bucharest, 1988
"Souness nearly killed him - it was horrific, one of the worst tackles I have ever seen," said Rotariu's teammate Gheorghe Popescu.
Harald Schumacher on Patrick Battiston West Germany vs France, 1982
Battison lost three teeth in this collision, which also left the Frenchman unconscious. Schumacher didn't even receive a yellow card.
Martin Taylor on Eduardo Birmingham vs Arsenal, 2008
Taylor received death threats after this tackle on Eduardo, which left the Brazil-born Croatian with a broken leg. He's always maintained it wasn't malicious.
Andoni Goikoetxea on Maradona Barcelona vs Athletic Bilbao, 1983
This studs' up challenge earned Goikoetxea his 'Butcher of Bilbao' nickname. It left the Argentinian with a severely damaged ankle.
Paul Gascoigne on Gary Charles Tottenham vs Notts Forest, FA Cup Final, 1991
Gazza injured himself, rupturing his knee ligaments, in this wild lunge at Charles. The Forest defender hobbled away.
Roy Keane on Alf-Inge Haaland
Manchester United vs Manchester City, 2001
Keane said in his autobiography that he had sought out Haaland, accusing the player of standing over over him when he injured his cruciate ligaments a few years earlier.
Lee Bowyer on Gerardo Leeds vs Malaga, 2002
"An act of serious assault," is how UEFA described Bowyer's stamp on Gerardo. The midfielder was later handed six-match ban.
Ben Thatcher on Pedro Mendes Manchester City vs Portsmouth, 2006
Mendes required oxygen at the side of the pitch after Thatcher hurtled towards him before smashing an elbow into his face. The City man was given an eight-match ban.
Ryan Shawcross on Aaron Ramsey Stoke vs Arsenal, 2010
Shawcross' mistimed tackle on Ramsey left the Arsenal midfielder out of the game for a year after he suffered a double leg break. The Stoke defender was visibly shaken afterwards.
Ryan Ledson on Lewis Baker Leeds vs Preston, 2018
This studs-up, two-footed lunge seen in a Carabao Cup clash earlier this season earned former Everton midfielder Ledson a red card.