Liverpool have set such high standards for themselves over the past few years that it’s always a talking point whenever they drop points these days.The Reds are currently on a four-match winless run in the Premier League following an emphatic 7-0 away win over Crystal Palace on December 19.Since then, Jurgen Klopp’s side have dropped points against West Brom, Newcastle and Manchester United. They also lost 1-0 away at Southampton.The reigning champions have scored just one goal in those four games (Sadio Mane netted the opener in the 1-1 draw against West Brom on December 27) and the team’s revered front three have struggled to produce their best form in recent weeks.Mane, along with Mohamed Salah and Roberto Firmino, have been unbelievably good over the past few seasons. Regardless of whatever else happens in the future, they will always be remembered as one of the best front threes that we’ve seen during the Premier League era.But is there a particular reason why they’re struggling to perform at the moment?p1escm6pg41vuk1vqi1dh84g21pqrh.jpgLiverpool legend Jamie Carragher attempted to answer this question live on Sky Sports’ Monday Night Football and his analysis was fascinating."When we talk about this Liverpool team, we talk about the front three," Carragher said. "It's almost like they come as a package."The reason I say that Liverpool's front three is unique is not that they are better than other front threes, it's how long they've stayed together.”Carragher showed some examples of other classic front threes (including Chelsea’s Duff-Drogba-Robben triumvirate and Man Utd’s legendary trio Tevez-Rooney-Ronaldo) and noticed how they only lasted a relatively short time together before they were broken up.p1escm29d4umhk511pdlu8mtf8b.jpg"They are now in their fourth season and the great front threes in the Premier League have normally only been together for two or three years,” Carragher continued."We're now in year four for Liverpool and we're maybe going to go into year five because they've all got two or three years left on their contracts."They are all getting to their late 20s and sooner or later that front three will have to be broken up."You can't, in two years' time, say 'we're going to buy a new front three' and replace them all. It will change over time."At this moment, I think Mane and Salah are going through poor form. It happens."I'm still confident that Mane and Salah will start scoring goals again, but I must say I am worried for Firmino."Carragher highlighted Firmino’s alarming drop in numbers - in terms of his ‘Possessions won final third per 90’ stats (down from 1.11 last season to 0.42 this) as well as his lack of goals (five so far this term).p1escm3660tvl1bv21tb910fig4jd.jpg"He's never been seen as the goalscorer, that's the responsibility of the other two," Carragher added. "But he's there to chip in and when they're not scoring, and I just feel he needs to be a bigger goal threat."Yesterday [against Manchester United], he had a couple of chances but he's not quite striking the ball right. His bringing players into the game has dropped off too."And also the counter-pressing and winning the ball back has dropped off with Firmino - and not just this season."I'm actually going back to last season, when Liverpool won the league. I was a little bit worried then and I was thinking, 'Can he turn it around this season?'"Carragher believes it won’t be too much longer before Liverpool’s revered front three are broken up and suspects Firmino could be the forward who goes first.p1escm52me15rdkpr25n1ef4f5hf.jpg"He was the best in the league at it, but it's a massive drop off, over 50 per cent from last season," the retired defender said."Last season, when he wasn't getting the goals and assists, you'd say, 'well, look at what else he's doing from the front'."I'm sure everyone's numbers for pressing have gone down this season, but that for me is a big drop."He's the one I'm worried about, whether it be a lack of form or maybe just that slow decline as you get a little bit older, which is natural for any attacker when they get to their late 20s because they don't play as long as players in other areas of the pitch."It's almost unprecedented, what Liverpool have done with their front three, how long they have been together and how often they play, and sooner or later that front three will have to be broken up."You can watch Carragher’s analysis of Liverpool’s front three (including Gary Neville's thoughts) in full here…