Sancho's first goal since September earned United a 2-2 draw at Old Trafford, after the home side had been trailing 2-0 until the 62nd minute.
The winger was playing for only the second time after a prolonged absence for his physical and mental wellbeing, but proved he could still play a big part this season with the crucial leveller.
"I am really happy he is (heading) in the right direction," Ten Hag said. "I hope he can keep his momentum going and I am sure it will strengthen him and motivate him even more. He is a brilliant footballer and if he can invest in the right levels he can be outstanding.
"We now have a team that can play in the opponents' half, he likes that, he can play in tight areas. It is in his own hands and so if he wants, he can do, and in this team, it is great to play...
"It is clear it is a difficult period but I am pleased and proud he did it so I will back him, the coaches will, and the team, but finally he has to do it himself."
Ten Hag was however frustrated that his side could not extend their home winning streak to 14 games in all competitions.
"I have mixed feelings," he added. "If you are 2-0 down, it may be wrong to be disappointed, but on the other hand you have to win this game when you see on the pitch the two teams and if you create so many chances.
"But if you start each half the way we did, it is unacceptable."
