In football, there are no friends, just acquaintances. It is a phrase you hear from professional players from time to time.
They use it to describe the transient nature of their lives, of what happens when a career hops from city to city, country to country, when the place you call home can abruptly change with one phone call in late August or January.
Some footballers spend years in a dressing room unable to speak more than a dozen words in the same language as a colleague, their only exchanges urgent exhortations on the field, the jargon of the workplace.
They can know intimately the technical capacities, the runs and the passes of a colleague and know almost nothing of his soul.
Of course there are some friendships, occasionally lasting and deep ones, formed in elite football, but even then teammates' relationships with their peers will be nuanced by the essential, competitive instinct that defines every successful sportsperson.
Witness the actions of Ricardo Carvalho last week.
Carvalho, an experienced, unusually poised, calm and mature central defender, stormed out of Portugal's training camp when he thought he would not be selected in the starting XI for the match against Cyprus.
He was furious that Pepe, his Real Madrid and Portugal teammate, was going to be picked ahead of him when, Carvalho imagined, his own fitness and readiness for the game seemed sharper.
Carvalho and Pepe will continue to line up together as excellent partners at centre-back for Real, but the incident simply showed the ever-present potential for jealousy that is part of most footballers' make-up.
Another experienced player walked out on his team last week. Steed Malbranque cancelled the two-year contract he had signed only a month earlier with Saint Etienne for what he and the French club explained only as "personal reasons."
The 31 year old, who spent 10 years in the English Premier League with Fulham, Tottenham Hotspur and Sunderland, had told Christophe Galtier, his St Etienne coach, he felt unable to take part in their last match against Sochaux.
Malbranque, a former France Under 21 international, had earlier seemed pleased to be returning to Ligue 1, where he began with Lyon.
Galtier heard few specific details from Malbranque about what was troubling him, but heard enough conviction in what the player said to feel it was unlikely Malbranque would ever play professionally again.
Outside the circle of Malbranque's intimates, nobody seems much the wiser as to what pressures he has been under. It needed a statement from his solicitors to deny several days of rumour that Malbranque had taken the decision because his son was suffering from cancer. Malbranque does not have a son.
The number of players in the Sunderland squad, who had shared a dressing room with Malbranque for three years, who did not even know that fact was surprisingly high.
Titus Bramble, a teammate of Malbranque's all last year, explained via the social network site, Twitter: "People saying we should have known if Steed has a son but Steed is a very quiet person so didn't talk about his family and what he did outside of work. When he did talk, it was only to do with football."
Bramble's confession of ignorance is a strong enough reason to curb any further speculations on the cause of Malbranque's decision.
What is true is that he has spent his working life in an intense, blinkered environment where young men coexist, talking "only about football", as Bramble put it, or at least mostly about football, while they prepare for afternoons and evenings where they will be obsessively scrutinised by tens of thousands of people, some of whom will shout loud enough that the players hear their insults and derision, as well as listening out for the gratifying sound of applause.
Across websites, strangers who watch their matches on television, their actions and errors replayed in slow motion and from multiple different camera angles, submit opinions and sometimes scorn on a 24/7 reel of blogs and tweets.
Professional football is glamorous, lucrative, a schoolboy's dream of a job. At the same time, it can be brutally unforgiving.
There is little space within the professional dressing room, for instance, to acknowledge private fears or insecurities. There is often little space even to be a nonconformist.
Javi Poves, a young Spanish central defender, attracted more attention during the recent close-season than he ever had as a professional rising through the ranks to his first division debut with Sporting Gijon last May.
In July, he suddenly announced he was quitting the game at 24, with a year of his €60,000-a-season (Dh318,000) contract to run. He had learnt to despise a sport that was "corrupt and dirty", he told reporters.
Poves can come across rather like a radical undergraduate, and certainly did to some of his teammates when he boarded planes for away matches clutching books by Karl Marx. But he evidently found a world, where, he says, "people look up to footballers far too much" deeply uncomfortable.
The hype around the game, partly driven by broadcasters, advertisers and sponsors, can easily turn players into two-dimensional cartoon superheroes or pantomime villains. It can obscure their human vulnerabilities.
On Tuesday, Hannover, of the German Bundesliga, released a statement, jointly with their goalkeeper Markus Miller, to say the 29 year old would be receiving treatment for "mental exhaustion". He referred to his feelings of inadequacy, and, with that, growing pressure.
Hannover as a club are unusually sensitive to the psychological strains on players.
In 2009, their goalkeeper Robert Enke, Germany's No 1 at the time, committed suicide. He had been suffering from depression, a fact he kept secret from colleagues and employers.
Enke's biography, A Life Too Short, based around diaries he had kept, will be published in English this month. It includes haunting accounts of his thinking during a career that included such highs as being signed by Barcelona and representing his country, and some lonely lows spent a long way from home.
During a strained period at Fenerbahce in Istanbul, Enke wrote: "I don't know why I agreed to come here. Probably because I thought I just have to feel needed and then everything will be sorted again. Unfortunately it is not so simple. The year in Barcelona has really changed me.
"I have let all the self-belief that I built up in three years in Lisbon [with Benfica] go. Right now, in this condition I am just not made for football."
By the month of his death, which he caused by putting his body in the way of a moving train, the diary was no longer being written in full sentences. One of the final entries simply said: "Only blaming myself."