Barcelona 1-0 Manchester United: Neymar punishes Antonio Valencia error as Red Devils lose the final match of their American tour

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One of the intriguing plots to this pre-season for Manchester United centres on their defence. More specifically, the centre of their defence.

Who will partner Eric Bailly at the heart of Jose Mourinho’s back four? The answer is not quite as clear cut as we might have imagined when Victor Lindelof was paraded in June, after United lost to Barcelona in this friendly.

He might have cost £31million but the Iceman could yet be left in the cold during the opening weeks of this campaign. Lindelof, Chris Smalling and Phil Jones are effectively on trial.

Neymar celebrates after his first-half goal gave Barcelona the lead against Manchester United at the FedExField

Neymar capitalises on a poor first touch Antonio Valencia to bare down on the Manchester United goal

United's Ecuadorian right back looks on despairingly as Neymar takes the ball away from him to score the opener

Neymar passes the ball home into the United net after getting it out of his feet with Messi watching on 

Manchester United's players look dejected in the background as Brazilian superstar Neymar wheels away to celebrate

Lindelof and Smalling were the pair to start Wednesday’s slender defeat by Barcelona and those 45 minutes were by no means easy before the changes were rung at half-time.

Barca’s main trio of Lionel Messi, Luis Suarez and Neymar are electric more often than not and some of their link-up at FedEx Field just goes to show what a problem replacing Neymar would be should he depart for Paris Saint-Germain in the coming weeks.

Nullifying one of them, let alone three, is a thankless task for the world’s best. Be it in a friendly or not, once the switch is flicked, Barca are just too good. So that United’s two kept going when Catalan tails were up is testament to their resolve.

Lindelof has endured a tough tour, at fault for two goals at LA Galaxy and guilty of a clumsy challenge to concede a penalty against Real Madrid. This was a real test and he improved.

The Swede certainly had his positive moments dealing with the mesmeric movement. There were occasions the 23-year-old read situations coolly. But offset by that was nervous decision-making and the failure to engage with markers, instead choosing to back off.

New signing Victor Lindelof had another testing time at the back against Barcelona's world class front three

Romelu Lukaku was relieved to see the flag go up after missing this glorious early chance for Manchester United

Five-time Ballon d'Or winner Lionel Messi takes on the Manchester United defence early in the first-half

Manchester United goalkeeper David de Gea barks orders at his defence after saving an early effort from Messi

Mourinho was particularly flustered by a lack of intensity, pleading with both Lindelof and Smalling to win the ball higher. There was also a scare when Lindelof misjudged Messi’s quick free-kick, sending Smalling the wrong way as he attempted to cover, leaving David De Gea to thwart Suarez’s acrobatics.

They came off having conceded one, a scrappy Neymar finish just after the half-hour which Antonio Valencia will not want to watch back after struggling to deal with Messi ball inside him.

United had threatened themselves. Paul Pogba and Marcus Rashford were standouts with a sort of directness United so craved for large parts of last season. Rashford’s delicious cross from the right after just three minutes was begging to be finished by Romelu Lukaku but over it flew.

Pogba already appears more vibrant as he approaches a second term at Old Trafford and forced Jasper Cillessen into a very smart stop from 30 yards. This was the Pogba of Juventus, drawing across a bouncing ball from Daley Blind’s throw. A meaty strike, the sort of which we are bound to see more of.

Lukaku rises to beat Sergio Busquets to the ball in a game where he was largely starved of service by Barcelona

Mancchester United winger Jesse Lingard goes down under a heavy challenge from Barcelona's Ivan Rakitic

Barcelona's Dutch goalkeeper Jaspen Cillessen was largely untroubled as the Catalans dominated possession

Rashford too went close, beating both Suarez and Samuel Umtiti on the byline while substitute Anthony Martial curled over. United seem to have added zeal going forward. More pace, an injection of energy missing previously. Their issues will not be creating chances.

The defence is an issue owing to the number of Mourinho’s options. Jones will believe he is showing enough to be considered, assured in the second half alongside Bailly, albeit without Barca's devastating matchwinners to contend with.

Lindelof arrived with a burgeoning reputation and will undoubtedly end up being Bailly’s long-term partner but whether that comes right away remains to be seen. The pair have only played alongside each other in a back three so far.

It is worth remembering that Bailly was told by Mourinho last summer that he was coming in as back up initially, that he would be afforded a chance eventually but not straight away.

Circumstances, and some tremendous performances thereafter, saw the Ivorian become United’s premier defender. Lindelof will hope similar awaits him but that is by no means a forgone conclusion.

One Manchester United shows his allegiance in a rather unique way by dressing up as a Red Devil

Marouane Fellaini - a half-time substitute - was booked in the closing stages for a foul on Carles Alena

Luis Suarez was the first to congratulate his team-mate after Neymar broke the deadlock