The lot of the football scout has never been an easy one. Geoff Twentyman, who once suggested Liverpool might hire a man called Bill Shankly, found himself forlorn and insecure when Everton's success became a threat to his club in the 1980s. The chief scout's judgment was first questioned when Ian Rush, whom he discovered, did not score in his first full season. A biographical gem on Twentyman by the writer and journalist Simon Hughes, Secret Diary of a Liverpool Scout, suggested the fact that Gary Lineker signed at Goodison rather than Anfield, hastened the end for a man so integral to the great Liverpool era.

Twentyman died in 2004 and heaven knows how he would have managed in the world of analytics brought to Liverpool when Damien Comolli was appointed director of football strategy in 2010 by the club's American owners, who are evangelists of that cause. It is a science in which players are judged by the vast array of statistics available these days and in which mathematical algorithms form a key part of the armoury.

The collision of these worlds is captured in a remarkable way by the writer and journalist Michael Calvin in a new book, The Nowhere Men, which feels like a desperately needed accompaniment to the madness of this summer – dominated as it has been by players on six-figure weekly salaries seeking to sling their hook.

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The book's revelations about the talent-spotting strategies of David Moyes, Brendan Rodgers and Arsène Wenger are revealing, but it penetrates deep beneath football's soap opera froth, into the world occupied by those you probably won't have heard of: men who, as Calvin puts it, "supply the star system but remain resistant to it".

Mel Johnson, Dean Austin, Paul Dyer, John Griffin, Gary Penrice, Dave Philpotts, Steve Jones and Terry Murphy are unknown to most people, though the way they buzz with talk, guard the identity of the game's best prospects and all seem to know each other suggests they are only innominate because the football circus that only promotes its stars makes them so.

The book deconstructs the opposition between old-fashioned hunch and new-fangled metrics as it reveals how Moyes has utilised the best of both worlds at Everton, as he surely will at United. Everton's head of technical scouting, James Smith, who has worked with Moyes since his Preston North End days, reveals in the book how the Glaswegian was the only manager outside the Premier League to use performance analysis when at Deepdale. Smith's testimony suggests Moyes's rigour is greater than has previously been appreciated.

In a secret recruitment room at his former club – "Everton's most valuable intellectual property" – the entire transfer strategy is mapped out on whiteboards covering all four walls. They include the "MOT Test" which Moyes devises for each scouted player under the age 24, each judged against a checklist of 12 criteria for each position. Moyes is very studious. One whiteboard features the favourite Premier League players of all his senior staff, with four names selected. Another board lists Moyes's notion of the best current starting 11 in each year running to 2014, with an insight into who will drop out and who might take a player's place. Another, smaller board features the most promising Championship, League One and Two players under the age of 23.

Though the whiteboards are evidence that scouting's "back of a fag packet" days are over, as Smith puts it, the scouts and the human element are still integral to the new methods. For that, the "Nowhere Men" are needed. The name of Jack Butland stood out on Moyes's lower leagues whiteboard, yet a night out scouting with Mel Johnson taught Calvin the painful limitations of viewing a player once.

Johnson, Liverpool's senior scout in the south, wanted to see the then Birmingham City keeper playing on loan for Cheltenham in the inhospitable environs of Roots Hall, Southend. The unravelling of Butland's game in a defeat that night, culminating in Calvin observing his "unconscious act of chewing the neckband of his shirt [in] a child-like gesture which radiated fearfulness and isolation" is agonising to read about. Johnson insisted it was not the real Butland and he should know.

It was when working at Tottenham for their former director of football Frank Arnesen that Johnson recommended Shrewsbury Town's Joe Hart, with the Shropshire club asking for £1m. "Frank said 'no'.

Arnesen was not the first or the last to ignore a "Nowhere Man". Fulham's chief scout, Barry Simmonds, got an earful from Roy Hodgson after urging the manager to watch Mousa Dembélé, now at Spurs, play for AZ Alkmaar. "What he didn't call me wasn't worth knowing," Simmonds says of the criticism levelled at him by Hodgson, who felt his night had been wasted. "It was only later, when he was managing Liverpool, that he called and said 'you were right weren't you…?'"

There are so many other scouts like him, who are busy networking and scouring newspapers, only for many of them to be ousted from clubs by the convulsions which come when a manager is sacked.

When that happens, "good people are suddenly disposable chattels", Calvin says.

The good news when Leicester underwent such upheaval was that Steve Jones got an email saying he was being retained. The bad news was the proposed take-it-or-leave-it salary of £50 a week. Jones left it. A brief spell at Hull ended the same way for him, when scouts were informed they would no longer be paid. That made Sheffield United's "salary" of 40p-a-mile expenses, to produce a 13-page opposition report on Colchester United, quite attractive to Jones.

Calvin calls these people the "mileage men". An inestimable number of players owe it to the veteran scout Griffin for pushing their careers on, from Stan Collymore to Alan Pardew, while Penrice's discoveries have included Paulo Gazzaniga, who went from the fringes of Valencia's third team to Southampton, by way of Gillingham.

The book reveals how Arsenal cling to old notions about the players they sign. Arsenal's Murphy – the club's former youth development officer who stuck with Martin Keown when the chief scout said "no" – carries around a piece of paper on which 32 "principles" found in a successful recruit are carefully listed.

The book relates the fates of Steve Gritt, sacked as Bournemouth chief scout and replaced by a video analyst; Russ Richardson, sacked as Bristol City chief scout and effectively replaced by the owner's son; Watford's scouts being cleared out en masse when the Italian owners walked in.

"Same old same old," the "Nowhere Men" will say. Twentyman exhorted Shankly to sign Terry McDermott and only when the midfielder was doing great things at Newcastle United did the error of judgement become clear.

"Aye, he was a cracking player," Shankly admitted. "We made a mistake on that one."

'The Nowhere Men, the Unknown Story of Football's Talent Spotters', by Michael Calvin. Century. £14.99

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