On Tuesday, at UCLA, Amad Diallo professed a wish to stay at Manchester United “all my life”. Twenty-four hours later, 130 miles south at San Diego’s Snapdragon Stadium, and the Ivorian filed a first-half display that was a fine audition to take him into Erik ten Hag’s first XI for a long while, at least.

The Ivorian was either the scorer (once) or provider (twice) in all of his team’s goals, these coming in an opening 45 minutes that will have impressed Erik ten Hag far more than the second, as shape and intent were lost.

And, again, there were two injury concerns, this time regarding Marcus Rashford, who took what appeared to be a stamp to the ankle and was forced off 64 minutes in. Later, Antony followed, and Ten Hag will pray the two widemen are fine because otherwise it will be four men down in only the second match of this US tour.

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The first two injuries came in Saturday’s 2-1 defeat to Arsenal and after Leny Yoro was confirmed as ruled out for three months due to the metatarsal injury suffered then, Victor Lindelof and Harry Maguire formed an old firm central defensive pairing that was supposed to be mothballed two or more years ago.

Into the berth vacated by Rasmus Hojlund’s hamstring pull in the same game – that rules him out for six weeks – stepped Jadon Sancho who had also operated at No 9 on last year’s tour of the States.

Soon, Sancho had the ball past the Real Betis goalkeeper, Rui Silva, after the menacing Diallo pulled a long ball down and played him in. But the finish, though adept, came from an offside position.

A similar move next had Diallo prodding a pass to Scott McTominay and as he galloped through a central channel Nobel Mendy yanked him down. It appeared an obvious infringement but the referee, Alexis Da Silva, was not interested.

Now, as the evening cooled, Betis struck and this was due to a Tom Heaton howler. Rodri, the Spaniard’s right-sided marauder, cut in from this flank and fashioned a cross-shot that the United keeper saved but also scooped back to the No 17. This time he picked out Iker Losada and as Heaton was on the floor and stranded the strike was simple.

Here, United had an air of an anti-calm that did not augur well. But, instantly, this and Betis’s advantage was wiped away. Diallo knifed into the opponent’s area, Romain Perraud toppled him, and Da Silva this time was interested.

The American official pointed to the spot and Rashford followed his stuttering-to-a-standstill run-up with a swish of his right boot and converted the penalty in the left corner, Silva allowed no chance.

The equaliser had derived from aggressive intent. So did United’s next two finishes as they pulled away from Manuel Pellegrini’s team and threatened a rout.

With Luke Shaw a perennial fitness concern and Tyrell Malacia still recovering from a serious knee injury, Harry Amass is hoping to become this year’s Kobbie Mainoo, at left-back: a youngster who can become a factor in the first team.

The cross he slid over for McTominay marked him out as having cute attacking intent. The ball, eventually, arrived at Diallo’s lethal left and he hammered in. 2-1 to United and they cruised.

Soon, there was further ruthlessness. Diallo, as with the penalty, the creator. A corner dinked in from the right by him landed at Rashford, who was beyond the far post: he turned the ball back to Casemiro and, inches out, he bundled home.

The newly elevated status of the Maguire-Lindelof axis was underscored by them being the sole removal for the second half by Ten Hag, who dare not have another malady at centre-back. Jonny Evans and Will Fish replaced them and were soon part of a porous rearguard that was nearly breached fatally at two Betis corners.

Then, a sight to hearten Ten Hag and United fans, as Sancho went on a blistering run that scattered Betis defenders before him in the type of act close to absent from his game since he joined.

Poorer tidings for Red Devils enthusiasts, though, was Rashford limping off in discernible pain and heading for the tunnel, a happening followed by Betis pegging United back, as Diego Lllorente, unmarked, rose to head beyond Heaton. Cut to the touchline and a remonstrating Ten Hag, unhappy that a raft of planned changes had not been allowed before the Betis strike.

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26,248 souls were in the outdoor 35,000 capacity venue and they were entertained, as shown by the casual yet incisive chip from one of Ten Hag’s changes, Toby Collyer, which had James Scanlon skipping along the right: he teed up Mason Mount (another replacement) but he blasted over.

A similar lack of composure came when Hannibal Mejbri darted infield and zoomed the ball into Ethan Wheatley: the centre-forward was in prime position, before goal, but the touch was blunt and the chance evaporated.

As the clock ticked down, Antony hobbled off. United’s treatment room is threatening to be full, even before the real stuff of the new season starts. At least Rashford could join the post-game thank you to fans conducted in a walk about by the players.