Two late goals from Declan Rice and Gabriel Jesus inspired the Gunners to a dramatic victory in a Super Sunday clash at the Emirates.
And Ten Hag insisted that Sancho was completely left out of the side due to his poor performances in training.
The United gaffer said: “Jadon, on his performance in training, was not selected.
“You have to reach a level at Manchester United every day and we can make choices in the front line. So for this game he was not selected.”
Sancho refused to keep quiet and took to Twitter to voice his opinion on the matter.
What did Jadon Sancho say about Erik ten Hag on Twitter?
Sancho, 23, put out a statement on Twitter saying: “Please don’t believe everything you read! I will not allow people saying things that is completely untrue.
“I have conducted myself in training very well this week. I believe there are other reasons for this matter that I won’t go into.
“I have been a scapegoat for a long time which isn’t fair! All I want to do is play football with a smile on my face and contribute to my team.
“I respect all decisions that are made by the coaching staff, I play with fantastic players… I will continue to fight for this badge no matter what!”
Why isn’t Jadon Sancho playing for Man Utd?
Jadon Sancho has been banished from Manchester United training after the public row with Erik ten Hag.
And the Red Devils have confirmed that the English winger is currently on a “personal training programme” pending a resolution of a “squad discipline issue”.
This has ruled Sancho out of the Brighton fixture on the weekend.