Barcelona's 3-1 home defeat to Real Madrid ahead of a testing trip to Juventus in the Champions League on Wednesday was a nasty little jolt to Ronald Koeman's previously robust sheen as the new manager at Camp Nou. The Dutchman's exuberant roll of the dice to start 17-year-old Pedri against La Liga's champions didn't work -- in fact, it flopped.

Fair play to Koeman though: when you roll the dice you can either win big or look daft. His other experiment with moving Philippe Coutinho out of the No. 10 position left the previously exuberant Brazilian trotting around to little effect when his team were on the offensive and making desultory efforts to get near his opponents when he was supposed to be tracking back, tackling or pressing. It was an extremely bad day at the office, followed by a muscle injury that will now keep Coutinho out for a couple of weeks.

Worst of all for Koeman, whose short reign had not only introduced a Pax Romana amid the strife, empire-destruction and blame-casting all around him at Camp Nou but had begun to spark Barca into playing with verve and sparkle again, he completely fluffed his lines when it came to making the much-needed substitutions. It was not simply 'too little too late,' but his complete failure to recognise Pedri and Coutinho's discordant performances, when it was glaringly obvious at half-time, was like listening to a man in boxing gloves playing a Mozart piano concerto. Fascinating ... but horrifying.

Nevertheless, adverse results -- even a 3-1 Clasico defeat that rubs salt in the wounds of one point taken from the previous six, against Getafe and Sevilla -- plus just one goal scored in the last 260 Liga minutes, are ephemeral. Unless things continue to spiral downwards, the sting can evaporate, lessons can be assimilated and the humiliation used as a thorn in the side to spur on a proud squad which is in the tricky process of re-construction.

And there was a short-term credibility boost for Koeman -- make no mistake about it. After just one year as a fully-fledged senior professional with Ajax, 19-year-old United States full-back Sergino Dest, the first American to ever play in the Clasico, was exceptionally impressive. If you started a list of the best players to emerge from that superbly watchable and quality-packed Clasico, then Dest would be the first Barcelona player named, no question. This is neither hype nor overexcitement.

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At Dest's age, establishing yourself in a squad searching for its identity during a tempestuous period -- which could yet end with Koeman being removed next May if Victor Font wins the imminent presidential elections and club legend Xavi is willing to take over -- is tough and form dips must be expected. Perhaps we won't consistently see the absolute best of this fleet-footed, highly competitive, attack-minded defender for a couple of seasons, when he'll be the grand old age of 21.

But what Dest showed against Real Madrid, who continued to flood five or six men forward even at 2-1 and 3-1 up, as Barcelona's midfielders gave up the chase, was enough to grab our attention. The American ended up as the third centre-back (with Gerard Pique and Clement Lenglet) in a 3-4-1-2 formation for the last 10 minutes and looked born to the role.

His abundant highlights against Madrid certainly helped Koeman's credibility. Barcelona, via their now departed head of football, Eric Abidal, had a previous arrangement with Norwich to sign right-back Max Aarons and add him to the increasing queue of 'so you want me to replace Dani Alves?' aspirants.

Aarons was understandably keen, his agent was doing shuttle-runs between the two clubs and the main debate was about whether the deal would become permanent immediately, be a loan 'on approval' scheme, or a loan deal with a guaranteed purchase price written in. Then along came Koeman. The Dutchman insisted that as soon as Nelson Semedo's €30m move to Wolves was completed it was imperative that Dest was signed for €21m and Aarons discarded.

Bayern Munich had also been linked with the pair but, until 48 hours before Dest was announced as a new Barca signing, the German giants were utterly convinced they would sign him. The European champions must have cursed the skies red, white and blue in disbelief when Dest's agents told Bayern sporting director Hasan Salihamidzic that their client preferred to join the club Germany's perpetual champions had just thrashed 8-2 en route to winning the Treble.

There had been a clue last year when ex-Ajax, Inter and Everton winger Andy van der Meyde, now working in TV, asked the emerging Ajax full-back whether he fancied life in Spain, and at which club? Dest answered: "I think it'll be better for me playing for Barcelona. Madrid is different -- they're more about all-effort and struggling hard to win. I see Feynoord-Ajax comparisons: Feyenoord is Madrid and Ajax is Barca." I guess it was written in the stars there and then.

Yet, with the Juventus match arriving on Wednesday, and given Pique's red card against Ferencvaros means he'll be watching from his sofa rather than going into battle against Alvaro Morata and Paulo Dybala, it might be that Koeman decides there's a place for Sergi Roberto's sizeable experience at right-back instead of Dest.

Pique's absence means that 21-year-old Uruguayan Ronald Araujo will likely partner Lenglet at centre-back, but in what formation? If Koeman is happy enough to revert to 4-2-3-1 because his three-at-the-back was just a Hail Mary attempt at the end of a losing Clasico when he wanted to flood the pitch with attacking substitutes (too late, Coach, FAR too late), then perhaps he asks Roberto to help chaperone Araujo and tells Dest to watch from the bench?

I hope not. It seems a risible idea given how well the U.S. international has performed since coming on at left-back for the injured Jordi Alba late in the draw against Sevilla three weeks ago. But you never know.

Alba raced back early from a muscle strain to try to repel Madrid and, in fact, created much of Barcelona's attacking threat including their terrific equaliser. He worked until he dropped and while he has not re-injured himself, the huge physical effort he put in followed by the briefest of recuperation time then a flight to Turin and a match against serially difficult rivals, might make the physios, doctors and Koeman ponder the idea of letting him start on the bench. As a result, Dest might again be asked to play left-back.

As a side note, if Araujo is chosen to replace Pique, it's going to be fascinating to watch the 21-year-old. Recently, Barcelona have become a brand name for buying and selling badly -- over €350m spent on Ousmane Dembele, Coutinho and Antoine Griezmann compared to what the three of them have given back for the outlay -- and, at a time when several players have been renewed for lengths of contracts which make no sense, at inflated wages, whomever can claim to have his fingerprints on the signing of Araujo for around €2m from Uruguayan side Boston River in August 2018 can stand apart from the line of dunces in that department.

The imposing centre-back has looked quick, athletic and increasingly confident at bringing the ball out from the back every time he's had significant first-team exposure. He has masses to prove and lots to learn, but it might be that in Araujo, and almost certainly in Dest, Barcelona have bucked their trend of splurging ridiculous sums on footballers who don't fit and are sold on for massive financial losses.

Perhaps a no-holds-barred night in Turin, under examination from the hard-nosed perpetual Serie A winners, even if they don't have Cristiano Ronaldo to call upon, will damage my prediction. But right now it's easy to see Wednesday being the start of Dest and Araujo playing together, successfully and enjoyably, for a very long time to come.