Marcus Rashford's scoring streak since the World Cup has been so impressive that it can almost be considered a drought that he has gone two Premier League matches without a goal.
The England international has only failed to score in three league matches since club football resumed last December, and United didn't win any of them. It only further highlights his importance to the team and the fact that if he fails to find the back of the net, then there aren't many other likely candidates to do so.
This presents a particular problem for United tomorrow, when they travel to face Real Betis in the second leg of their Europa League last-16 tie.
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United head into the match with a comfortable three-goal lead from last week's meeting, in which Rashford scored, though Ten Hag will be well aware that his side aren't home and dry yet.
Alejandro Garnacho will miss the match through injury, meaning United are depleted of one squad option should they wish to rotate, though that doesn't mean they shouldn't.
Rashford squandered two good chances in the weekend draw with Southampton, showing signs of fatigue with poorly-executed shots that were easily saved. The first was fired awkwardly straight at Gavin Bazunu from a tight angle on the left, while the second was squandered after a sloppy first touch allowed Southampton's goalkeeper time to come out and smother the ball.
It is a huge compliment to Rashford that these two rare instances of rustiness were so noticeable, but it does indicate that this is a player who is showing real signs of burnout amid the insane fixture schedule. He has played 47 matches already this season for both club and country, and that could reach as many as 70 depending on his involvement over the international break and United's cup progression.
Rashford has only missed four matches he was eligible to play in all this season, all coming as a result of a muscle injury in September, and hasn't even had the luxury of being an unused substitute in any match at all. The rule is: if he's fit enough to play, he does.
It shows how over-reliant United are on the 25-year-old's talent that they haven't afforded him any rest at all this season, but soon there has to come a time when Ten Hag accepts that it is better for the team if their star player is left out.
There is perhaps no greater case for this than against Betis tomorrow night, with Rashford surely better off with a place on the bench given their three-goal cushion, and only brought onto the field as a last resort if things start to go badly wrong.
Rashford remains their greatest attacking threat, but Thursday night will be more about keeping them out at the other end than scoring themselves.
That match in Betis will come exactly a week before England begin their European Championship qualification campaign away against Italy, another night in which Rashford will most likely be relied upon.
It is hard to see any better opportunity to give the academy graduate some meaningful rest, and now Ten Hag must take it for the greater good of the campaign.
Rashford has been the standout player this season, and United have a duty of care to make sure he remains available until the very end.
Ten Hag must be a rule-breaker.
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