Eight successive wins for the first time since Ole Gunnar Solskjaer made such a brilliant start to his tenure in the middle of the 2018-19 season is a decent way for Ten Hag's side to approach the latest Manchester derby.
This triumph was achieved with a team missing at least seven players expected to be part of United's starting line-up against City, with expectations high they will avoid the chastening first-half endured at Etihad Stadium, when they trailed 4-0.
The progress since then has been immense. And, in Antony, they have an £81.3m winger who has now scored in successive games and brings trickery to wide areas straight out of the United tradition.
The Brazilian's first-half opener owed much to Diogo Dalot. The Portugal full-back did not last the opening period due to injury but it was his off-the-ball burst into the Charlton penalty area that created the space for Antony to curl a superb effort from Fred's square pass into the far corner.
Fred smacked a thunderous shot against a post and Christian Eriksen brought an excellent save out of Ashley Maynard-Brewer before Rashford extended his scoring streak.
First he swept home a pass from debutant Facundo Pellistri before he beat Maynard-Brewer in the final minute of stoppage time with a precise finish.
The England man is arguably in the best form of his career and Pep Guardiola already knows the damage he is capable of inflicting on a City defence that will need to be on its guard every bit as much as their hosts'.
Antony's superb first-half opener gave United the advantage but Dean Holden's visitors claimed plenty of credit for the way they continued to battle until second-half substitute Rashford found the net for a sixth successive game with goals in the 90th and 94th minutes.
Charlton's 9,000-strong travelling support, their largest ever for a midweek cup tie, applauded their side off, having backed them throughout, briefly raising hopes of an equaliser when Scott Fraser curled his free-kick straight at Tom Heaton.
For United, it means eight wins on the trot and a third last-four appearance in this competition in six seasons since they won it in 2017 under Jose Mourinho, their last domestic silverware.
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