Comment: Easy for Guardiola and Klopp to sympathise with Rooney when he's not theirs
When Jurgen Klopp was bemoaning Daniel Sturridge's inability to stay fit last season, it would have been interesting to see his reaction if, with the striker potentially eight days away from making a comeback in an important match for the club, he was pictured looking bleary-eyed at 5am on a night off.
Perhaps the Liverpool manager would have laughed and regaled the media, as he did last week, with the story from Mainz when he dressed up as Santa Claus and was photographed after having a few too many drinks. The story was immediately filed in the priceless/hilarious category of anecdotes.
"I feel for the players. We are all on the sunny side of life, earn a lot of money, do the job we love, but in the end there is a human being behind," Klopp might have said of Sturridge, as he did last week when asked about Wayne Rooney's (below) drinking incident.
"This generation is the most professional generation of footballers we've ever had. All the legends you still love, all the guys you still admire, drank like devils and smoked like crazy and were still good players."
Maybe Klopp would have looked to the "human being behind" Sturridge if he was having the worst season of his career, looking unfit and having pictures taken with strangers wearing his Liverpool kit at a wedding reception. Maybe, but it's probably best for Sturridge that it didn't happen.
Klopp, after all, is a man who recruited Liverpool's first full-time nutritionist and, as revealed by Chris Bascombe on Saturday, "players have been enrolled on food education courses and provided with tailor-made nutrition programmes".
Many of the legends that we all loved in the past may also have eaten tomato ketchup like devils and eaten eggs like crazy before a match while still being good players, yet Klopp has still banned both from the Liverpool canteen.
The club also re-arranges the order of food stations in the canteen depending on the nutritional needs of the week and assesses a player's diet based on their position and metabolic output.
"Players can coast by without thinking about nutrition - I've seen that," said Ted Munson, a performance nutritionist who works closely with the club.
"But they're missing out on maybe five to 10 per cent, particularly at a time where a game could be won or lost in the last 10 minutes."
With all of this effort to eke out every last drop of performance from players, Klopp's reaction to an under-performing star looking half-cut is unlikely to have been so jovial if it was one of his own.
Of course, Klopp is absolutely right to look for every small margin that is available, but it's indicative that so many foreign coaches can be seen as gurus simply because they ask professional players in the Premier League not to drink or eat things that are bad for them.
In the past, foreign players reacted with shock and bemusement to the levels of alcohol consumed by their British and Irish team-mates and Arsene Wenger was put into the Voltaire category of football thinkers in Britain when, in the 1990s (imagine!), he banned alcohol from the Players' Lounge.
Klopp has now taken the 'Foreigner with Funny Ideas' mantle along with Pep Guardiola, who received plenty of coverage for his apparently remarkable City transformation, much of which was based around professional athletes being at their optimum weight to perform and banning them from training if they weren't.
Given that he returned on Saturday from several months in the wilderness for not reaching his manager's standards, it would have been interesting to hear Yaya Toure's thoughts on Guardiola's comments about Rooney, which, like Klopp, were remarkably sympathetic to an out-of-form player at a rival club.
"I was lucky there were no pictures," the Manchester City manager said of his time as a player.
"I won't comment on the private lives of others because I don't like it when people comment on my private life. Everyone is entitled to a private life, so we have to respect what other people do."
The private lives of Guardiola's own players, however, is a different matter. Having already banned orange juice because of its high sugar content and pizza, for obvious reasons, Guardiola encourages his players to be asleep before midnight. This means, as Samir Nasri revealed last week, that they are effectively banned from sex after 12am even if they have the following day off.
In a slightly bizarre press conference moment, Guardiola clarified that he had no intention of banning sex altogether, but the impression remained that anyone doing it at 1am and then refuelling by ordering a Domino's would face his wrath. At least, hopefully, there would be no pictures.
In public, at least, Rooney has been backed by Jose Mourinho, who insisted on Friday that his captain was fit and ready to play against Arsenal, but with his first-choice striker suspended, Rooney was still left on the bench for an hour.
Many current and former players recalled their playing days when this sort of thing was the norm, but the whole point is that at the elite level which Rooney is meant to be at, as demonstrated by Klopp and Guardiola's nutritional demands, it's not the norm any more.
Rooney feels that "what's been going on is disgraceful", according to his defiant interview on Saturday and in terms of trying to portray the incident as some sort of national scandal he is correct.
He added: "It feels as if the media are trying to write my obituary and I won't let that happen... I'm proud of my achievements to date, but have not finished yet."
Yet, in order for him not to be finished, something needs to change for a player who struggles more than most, for whatever reason, to regain his fitness when not playing regularly.
Tony Adams and Roy Keane were exceptional players, but both cut down their drinking and had some of the best seasons of their stellar careers when older, but sober. Rooney could do worse than seek their advice about the best way to prolong his career.
At 31, Rooney is old enough to know better, but given how easily those questioning his professionalism have been labelled sanctimonious or pious, the most important thing that he'll learn - especially if he has no interest in changing is ways - is to make sure he doesn't get caught next time.