Erik ten Hag is tying himself in knots with baffling Manchester United policy nobody understands

That sound you could hear a little after 10pm on Thursday night in Greater Manchester was the collective noise of jaws hitting the floor when Erik ten Hag said he withdrew Marcus Rashford at half-time against Porto because "we have to rotate".

It was one of the more baffling decisions the Dutchman has made in recent years and although there was some gentle criticism of Rashford to follow, he continued to insist he hadn't taken United's best attacking threat off because of his defensive efforts.

Had Ten Hag done so, then it would have been more understandable. United's first-half defending was shambolic and Rashford was passive in letting Joao Mario run off him to send in the cross for the first. Diogo Dalot, struggling at left-back, probably needed more defensive support from Rashford.

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But the 26-year-old had scored one goal, set another up and was easily the most dangerous United forward on the pitch. He was playing with a zest and confidence we have started to see more of this season and his return to form is one of the few positives on the horizon.

Ten Hag's explanation for the substitution suggests it was pre-planned and that he always intended to bring Alejandro Garnacho on for Rashford at half-time. If that is the case it speaks of a lack of adaptability during a match. Ten Hag said he wanted Rashford fresh for Aston Villa, but the first priority was the game taking place at the time, one which you had established control of before throwing it away.

That isn't the only reason Ten Hag's 'rotation' policy is raising eyebrows this season. He has twice raised the issue of rotation now and on both occasions, it was taking an in-form Rashford out of the team. That isn't to suggest there is an issue between the pair and Ten Hag is right that a draining season will require rotation, but it needs to make more sense than it is doing.

Rashford hasn't played 90 minutes for more than a month now and after Sunday's game at Villa Park, he will get the international break off, while Garnacho will jet off to South America with the Argentina squad. Garnacho has played 90 minutes twice since Rashford last went the distance.

Rashford is actually getting plenty of time off. He played 73 minutes against Southampton, 63 minutes against Barnsley, 29 minutes against Crystal Palace, 79 minutes against FC Twente, 73 minutes against Tottenham and now 45 minutes against Porto.

That puts Rashford sixth on the list of most-used players this season at 685 minutes. United have played 10 matches and Rashford has played the equivalent of 7.6 matches. Garnacho and Amad both come in at 6.0 matches, having played 536 and 541 minutes respectively. It's not a big discrepancy.

The rotation policy also seems to only be aimed at the front three. Bruno Fernandes has looked in need of a rest for a while but has 798 minutes already and has featured in every game. Dalot is having a torrid time at left-back but has played 903 of a possible 930 minutes.

What makes those decisions even more bizarre is that Dalot and Fernandes were the most-used outfield players last season as well and by a long way. Dalot played 4,364 minutes and Fernandes 4,284. Garnacho was next on that list but played more than 700 minutes less than Fernandes.

Ten Hag has already labelled this season the "survival of the fittest" and a rotation policy is the right way to try and deal with that, but as with so much that is going on at the club at the moment, it just feels confused. When Fernandes is playing as often as he is, why was he given 30 minutes against Barnsley when the score was already 5-0?

It's easy to have sympathy with Dalot this season, forced to play out of position on the left, but the refusal to consider using Harry Amass even off the bench, or to rotate with Noussair Mazraoui and use a stop-gap on the right or left is making the situation worse.

Ten Hag certainly has more options in attack than he does at full-back, but there have been chances to rotate this season, just as there have been with Fernandes.

Maybe United wouldn't have won the game if Rashford had stayed on the pitch, but you can be sure Porto's defenders would have been happy to see him go off.