THERE’S loads of running involved in football you know, writes MATT KENNY. Absolutely loads. More running in a 90-minute period than most of can even hope to do in a week. And that’s before they even have to worry about being good at football and all that goes into being even remotely decent at it.

I’m not even good at running when I go for a run, let alone be dead good at running as well as picking up your man, picking a pass, thinking about your next move… I’m tired just thinking about it.

It’s bloody difficult work and no players have it tougher in the modern game than full-backs.

Full-backs have got a real rough deal these days; being asked to wear all sorts of different hats. While once you could get away with not straying beyond the halfway line, blocking crosses and marking the far post, you are now expected to be able to overlap constantly, provide an option, beat your man and chip in with goals and assists on occasion.

Oh and all that defensive stuff you used to have to do? Don’t forget about that after you’ve finished doing the wide players’ jobs, because they’re all off in the middle of the park playing number 10.

Football - FA Premier League - Newcastle United FC v Liverpool FC

Roberto Carlos was a relentless attacking force down the left, combining speed and power with devastating shots. Lilian Thuram was a rock of a man — you shall not pass, but when he took the ball from you, you better believe he could pass.

Both men were great, both completely different types of full-back. Since they retired, demands on players have grown substantially with an increasing want for right and left backs who can do everything.

So you can see why Liverpool have found it so hard to find outstanding full-backs over the years.

As an 11-year old, I thought John Arne Riise was brilliant. He smashed in a few goals here and there, ran fast and did some sort of weird, inverted Ravanelli celebration.

Only when I got older did I realise the error of my ways and grow sick of the bloody sight of him.

Riise had his moments, some that we can all still enjoy now, but objectively he was a rubbish left back with severe limitations who became increasingly exposed as the game progressed. Kicking it dead hard doesn’t cut it anymore and when you’re playing in India because Fulham and some Cypriot team don’t want you, you know it’s time to pack it in and model pants for a living. As it is, he’s back with his first club Aalesund in Norway. But the pants are in the post.

FRIBOURG, SWITZERLAND - Saturday, July 19, 2008: Liverpool's Fabio Aurelio warms-up during a pre-season friendly match against Wisla Krakow at Stade St-Leonard. (Photo by David Rawcliffe/Propaganda)

Then there was Fabio Aurelio. Ahhhh, Fabio. He had everything Riise lacked — composure, class, vision, awareness and the ability to run in more than just straight lines.

Aurelio was the type of footballer who further adds to the stereotype that all left-footed players have a magical ability to do whatever they want with the ball at any time. A player with real technical prowess who was also competent without the ball and the closest Liverpool have come over the last 10 years to having a great left-back.

Unfortunately, Fabio lacked the one thing that is essential for a modern full-back and cannot be taught on the training ground: functioning joints and limbs. Having a wand of a left-foot is all well and good but if your legs are falling off every six weeks then it’s no real use to anyone. A massive shame.

Dossena, Insua, Konchesky and Enrique all tried and failed (some spectacularly. Hi, Mrs Konchesky!) to make the position their own, all too often displaying their shortcomings and limitations.

Which brings us to the Reds’ current left-back, Alberto Moreno.

Signed from Sevilla by Brendan Rodgers in the summer of 2014, the Spaniard was seen as a typical FSG buy. Young, full of potential and capped by his national team, at £12million Moreno had room to develop into one of the brightest full-backs in Europe with the right coaching.

Early signs were good, as Moreno scored a superb solo goal at White Hart Lane with a strike reminiscent of Riise’s Goodison effort from 2001.

In many ways Moreno has resembled Riise; pacy, direct, single-minded in his desire to attack, but also very one-footed and liable to errors.

As time went on, these errors crept into Moreno’s game more and more and with Liverpool’s defence looking more vulnerable every week, it was the Reds’ number 18 who eventually made way.

From that point onwards under Rodgers, Moreno would not get much of a look in despite the goals against column making equally grim reading in his absence.

Moreno was looking like yet another left-back set to be added to the Anfield scrapheap — until the arrival of Jürgen Klopp, who appears to have given him a new lease of life. Since the German was appointed, Moreno has started the vast majority of games and appears to have made the position his own.

Yet, despite having the faith of his manager, Moreno continues to divide opinion and still doesn’t completely inspire confidence defensively.

His statistics going forward, however, are hard to argue with and since the turn of the year he has notched up more assists (he has eight for the season so far) than star man Philippe Coutinho.

With the Reds lacking pace and the manager demanding a high-speed, high-intensity style it is easy to see why he would favour Moreno. But Klopp will be aware that the defence is still struggling and with rivals Leicester winning the league with steady-Eddie full-backs like Fuchs and Simpson, he could be forced to change his thinking.

On the evidence so far, it’s hard to decide whether Moreno is destined to be yet another failed Liverpool full-back or if he is the solution we’ve long sought after.

Last month, Klopp was hailing the best performance he had witnessed from Moreno after the full-back’s goal against Stoke. Last week, he was wondering where the left back was as Villarreal stole a win in Spain.

Maybe the 23-year-old, capped three times by Spain, is being judged too harshly and modern full-backs are simply being asked to do too much, with errors inevitable. That won’t matter to Klopp if he believes he can find a suitable upgrade — behind that smile is steel — which makes the remaining games key to Moreno’s Liverpool future.

It’s a bloody difficult job but somebody’s got to do it. Whether Moreno is close to clocking out for good or making the position his own remains to be seen.