It was last month that Ronald Koeman revealed he substituted Matthijs de Ligt for his own good. At fault for both of Germany’s goals in a 2-2 draw, the Netherlands defender was taken off at half-time to spare him any more humiliation, just days after an unconvincing showing against Bosnia & Herzegovina.

“It just looks like he is now in a period where all his mistakes are being punished,” said Koeman, the Netherlands coach. “I gave him a new chance but eventually protected him by taking him off.”

Three weeks on, Erik ten Hag has now found himself resorting to similar, drastic measures with his new £42 million signing from Bayern Munich, who endured a calamitous evening as Manchester United drew 3-3 with Porto.

Arguably the poorest of a very bad bunch in Sunday’s shambolic 3-0 defeat at home to Tottenham Hotspur, De Ligt somehow found further to fall here in Porto; bullied, bamboozled and ultimately beaten down by Porto’s raw but relentless 20-year-old striker Samu Omorodion.

You know things have not gone too well when a manager feels obliged to withdraw both of his centre-backs at the same time and that was the ignominy to befall De Ligt and Lisandro Martinez with 12 minutes of normal time remaining at the Estadio do Dragao.

Disastrous duo both hooked off early

Martinez had one of his most disappointing displays in a United shirt but the Argentine is usually far more dependable than this. Maybe the burden of trying to marshall a hapless De Ligt through this game did for him, too.

Coming just four days after that shellacking by Spurs, this was a case of out of the frying pan and into the fire for the Dutchman, his substitution an almost merciful act by Ten Hag, much as Koeman had also intended it to be.

There were doubtless plenty among the 2,500-strong travelling United supporters – minus those whose flight to Portugal had been cancelled earlier in the day – who will remember the time when another strapping centre-back arrived at Old Trafford and had a pretty awful time of it to begin with.

Nemanja Vidic, of course, recovered from inauspicious beginnings to establish himself as a United legend so it would be prudent not to form too many definitive judgements about De Ligt just now, particularly given that he is playing in a strange, chaotic team prone to extraordinary self-sabotage.

Yet there is little doubt the 25-year-old is struggling badly: for form, for confidence, for belief and any real sense of what he should be doing. His dire positioning and inability to smell danger and read the game were brutally exposed against Tottenham and here he seemed perpetually half a yard – or more – off the pace, unable to cope with the speed and physicality of Samu and, perhaps most troublingly, seemingly cowed by that challenge.

For the first goal, he could have cleared the ball long before it was delivered into the penalty area for Porto to score but elected to chest the ball to no one in particular.

With the second, he never looked like getting to the ball ahead of Samu, who headed home Joao Mario’s cross and it was much the same for the third goal, standing off the Porto striker as he rammed home Pepe’s squared pass.

Even when Samu’s first touch failed him a little later, he was still able to get off his shot and draw a fine save from Andre Onana because a fearful De Ligt was so reluctant to engage his opponent.

It is hard to see how Ten Hag can start with De Ligt against Aston Villa on Sunday after the week he has had. Harry Maguire was one of the centre-halves alongside Jonny Evans introduced at the expense of De Ligt and Martinez and he cast aside the disappointment of being told he had been left out of the England squad to claim a dramatic stoppage-time equaliser. Maguire should start alongside Martinez against Villa.

Bayern opted to sell De Ligt in part because Vincent Kompany was unconvinced he had the pace, mobility and reactions to play a high line. Dayot Upamecano and Kim Min Jae were preferred instead.

Yet anyone who watched Ollie Watkins up against Upamecano in Villa’s 1-0 win over Bayern in the Champions League on Wednesday will note what a torrid time he gave the defender, who was lucky to still be on the pitch for the second half.

And the concern for United fans is what Watkins might do to De Ligt in this state of mind. He needs to be taken out of the firing line.