Every successful team needs them, and Liverpool are no different.
And for all the fantastic goals, pretty passing moves and superlative saves, there's nothing that gets the crowd going quite like a full-blooded, meaty challenge.
Oh, and the occasional head-to-head with an opposing player, often sparking a flashpoint as fondly remembered as any action on the pitch.
We are talking hard men, and the 10 most celebrated tough guys to pull on a shirt for the Reds.
Warning: this list is not for the faint-hearted.
Graeme Souness
Younger fans may know him as that grump bloke on Sky Sports. Slightly older supporters will recoil at much that went on during his tenure as Liverpool boss.
But for those who saw him in action, Souness will forever be the driving heartbeat of the Reds midfield in the late 1970s and early 1980s, one of greatest and toughest players in the club's history.
His pinnacle came as skipper in the European Cup semi-final at Dinamo Bucharest in 1984. Having had a slight disagreement with a Dinamo player in the Anfield first leg - well, he broke his jaw - Souness was verbally and physically abused by Romanian players throughout the return match.
The Scot stood firm, though, and responded with an outstanding display in which he set up Ian Rush for the opener in a 2-1 win.
Kevin Sheedy, once on the books at Liverpool before moving to Everton, sums it up best. "I nutmegged Souness once in training," he said. "He just laughed, but then a few years later I did the same thing against him in a match and he elbowed me in the face."
Tommy Smith
The Anfield Iron earned his nickname for a reason. "Tommy Smith wasn't born, he was quarried," was the famous Bill Shankly quip about a player born within sight of Anfield and who forged a fearsome reputation at centre-back and later right-back.
Remarkably, for a player known for his very robust nature, Smith was only booked twice and sent off once for Liverpool - for dissent. Mind you, that perhaps wasn't a surprise given his usual welcome to opposing strikers was "you go past me and I'll break your f***ing back".
"Take a walk around my centre-half, gentlemen, he's a colossus!" said Shankly when unveiling new signing Yeats to the press. The Scot would become a Liverpool great, the first Reds captain to lift the FA Cup, and a man not to be trifled with on the pitch.
"I always knew if there was going to be a battle I would win the battle," said Yeats. His centre-back partner for much of his career? Tommy Smith. Good luck against those two.
Gerry Byrne
Not many players can play almost an entire FA Cup final with a broken collarbone. But then not many were like Byrne who, in the days before substitutes, had no option but to carry on against Leeds United in 1965.
The toughest of left-backs, future hard man Tommy Smith was given a taste as a 15-year-old in training when, having nutmegged Byrne moments earlier before scoring, he was left with a badly gashed eye after challenging the same player for a high ball.
"Lesson number one," said Shankly. "Never nutmeg Gerry Byrne, son, and think you can get away with it."
Steve McMahon
The Liverpool side that won three league titles and two FA Cups in the late 1980s caught the eye with its flowing football, but the steel came from McMahon, a central midfielder who wasn't averse to putting it about. Regularly.
"I'd kick my own brother if necessary... it's what being a professional footballer is all about," said McMahon, who Wimbledon's infamous Vinnie Jones declared as "his only real rival" to the tag of hardest man in football at the time.
The tackling from the Allerton-born midfielder was even more fearsome than his shooting at times, a regular feature in the side for six years after making his debut in 1975.
"I won't say he was dirty but certainly the hardest opponent was Jimmy Case," said former Manchester United skipper Bryan Robson, also not averse to putting the boot in. "He could certainly look after himself."
Jamie Carragher
Carragher echoed Byrne some 38 years later when he attempted to play on for a while at Blackburn Rovers despite suffering a broken leg.
The Bootle-born player was an uncompromising figure for almost 16 years, a defender's defender in every sense.
Said Steven Gerrard: "I always felt more secure, I felt more invincible being in front of him because I always knew what I had behind me, I knew I had a leader and, well, a mouth!" Just ask Philipp Degen.
Steven Gerrard
Arguably the finest player ever to appear for Liverpool, the Huyton-born midfielder's calling card during his early days was the type of no-nonsense, full-blooded challenge that remained a part of his repertoire throughout his career.
His total of seven red cards - two each against Everton and Manchester United - is more than double any other Reds player.
The Welshman would be the first to admit he wasn't the most technically gifted footballer. But what he lacked in pure talent he more than made up for with raw enthusiasm and tackling. Lots and lots and lots of tackling.
That uncompromising style made the left-back feared among wingers and hugely popular with Liverpool supporters, leading to arguably the most famous banner in the club's history. "I think they knew that deep down, I was just one of them," said Jones, a boyhood Red who lived the dream. With a lot of tackles.
James Milner
Modern rules mean the old-style hard man has become a thing of the past, but don't be fooled into thinking players aren't tough.
Milner is a case in point, able to play a season for Liverpool at left-back - despite not really wanting to - and then re-establishing himself in midfield, claiming some famous scalps along the way.
"You're a donkey," said Lionel Messi to his face, perhaps passing on a message from similarly irked former team-mate Neymar earlier in last season's Champions League campaign. Milner had the last laugh.
And honourable mentions to...
Virgil van Dijk isn't someone to trifle with, Ronnie Whelan was more than just good positional play and important goals during the 1980s, Bruce Grobbelaar fought in a war, Dietmar Hamann played part of the Champions League final in 2005 with a broken foot, Javier Mascherano became Rafael Benitez's Tasmanian Devil, Paul Ince could start an argument in an empty room while Neil Ruddock was, well, Neil Ruddock.