Unless Ten Hag drops Rashford from his team, starting with Wednesday's Premier League clash against Chelsea at Old Trafford, it will erode his reputation as a coach who is prepared to take the toughest decisions.
Sanctioning Cristiano Ronaldo's exit from Old Trafford a year ago was heralded as a sign of Ten Hag's determination to assert his authority on his squad, but parting with a player who had publicly lambasted his management and the club was relatively easy. The same applied to allowing David de Gea to leave as a free agent in the summer following a string of goalkeeping errors. Getting tough with those two was straightforward because the exit door was already open for them.
But Rashford is different. He is United's highest-earning player, for one thing, after signing a five-year deal worth a reported £325,000-a-week in the summer. He is regarded by the club hierarchy as the embodiment of United's proud record of giving local youngsters the chance to become stars at Old Trafford. If Ten Hag can't crack the code with Rashford, there is no easy way out for either the club or the player.
Rashford's dismal performance in Saturday's 1-0 loss at Newcastle United was condemned by a raft of former players including United greats Roy Keane and Paul Scholes, while Alan Shearer and Jamie Carragher also weighed in with critical comments while working as pundits at the weekend. That result meant that Newcastle moved above Man United into sixth place in the table.
Ten Hag has run out of reasons to persevere with Rashford. His goals have dried up and his work-rate diminishes by the game. Newcastle's Anthony Gordon, who could yet take Rashford's England place at Euro 2024, exposed Rashford's lack of industry with a display of tenacity and hunger before scoring the winner for Eddie Howe's team.
Taking Rashford out of the starting XI now will make United a better team, but also help the 26-year-old. It would, or should, allow him the opportunity to re-focus and rediscover his best form. After all, it was earlier this year that he equalled Dennis Viollet's 64-year-old club record of scoring in nine consecutive home games, and scored 10 winning goals in a season, during a campaign in which his post-World Cup form fuelled United's surge into the top four and Champions League qualification.
Rashford ended last season with 30 goals in all competitions, but his form has taken a nosedive in recent months and he has managed to score just twice in 18 games for United so far this term: one of those strikes was a penalty at Everton last week ,when captain Bruno Fernandes let him take the spot kick to help boost his confidence.
Ten Hag has deployed Rashford in every position across the front three with little to show for it. The player was clearly unhappy with playing in a central role while the club waited for summer signing Rasmus Højlund to find full fitness. He has recently played down the right, due to Alejandro Garnacho impressing on the left. But even when he was switched to his favoured left-sided position, Rashford failed to deliver.
Rashford's abject performance at Newcastle, when he offered nothing in attack and repeatedly failed to track back to halt full-back Tino Livramento's run, prompted Ten Hag to substitute him early in the second half. Rashford reacted with a look of surprise before slowly walking off, but perhaps the surprise was that he hadn't been taken off sooner.
Ten Hag's problem is that if he perseveres with Rashford, it will send a message to the rest of the squad that not every player is judged on performances. Centre-back Raphaël Varane has been dropped in favour of a revitalised Harry Maguire, winger Jadon Sancho has been ostracised by Ten Hag for refusing to apologise for a social media outburst after being dropped while summer signings Sofyan Amrabat, Mason Mount and Sergio Reguilón have all struggled to earn a starting spot when fit.
Rashford's lack of form has so far been overlooked by Ten Hag, who has spoken about "helping" the forward back to his best. But what is Rashford's best? Is it the hot streak of form that we saw for three months after the World Cup or should he be judged over a longer period? Since the start of the 2021-22 season, Rashford has scored 37 goals in 106 games in all competitions for United, which is a fairly average return for a player of his reputation. By comparison, Mohamed Salah has scored 74 in 122 games for Liverpool, while Tottenham Hotspur's Son Heung-Min has scored 47 in 107 appearances during the same period.
Rashford's run of 17 goals in 19 games after returning from the World Cup last season paints a picture of a prolific goal scorer, but that sequence now looks nothing more than an outlier within a longer period of under-performance. But those goals undoubtedly helped Rashford earn his lucrative new contract, despite a lack of clubs testing United's ability to hold on to him.
Maybe he has become too comfortable at United, too indulged by a club that has endured so many problems on and off the pitch that senior figures don't want to be confronted by the prospect of their star player becoming a problem. Sources have told ESPN that Rashford can be an aloof and detached figure around the club. One example came last season when he arrived late for a media interview ahead of the Carabao Cup final and kept his car engine running at the training ground while briefly speaking to the reporters waiting to see him. His demeanour at Newcastle was another low point which did little to portray Rashford in a good light.
But if Ten Hag overlooks the lack of goals, the poor performances and Rashford's questionable body language by keeping him in the team, it will send the wrong message. If the manager bases team selection on form and contribution, his decision on Rashford this week has become a litmus test of his readiness to make the big calls.