United’s Europa League win rounded out their group stage campaign, with Cristiano Ronaldo laying off the assist for the youngster’s 17th-minute strike.
“Let’s look at the positives from tonight. We have an extra player with Garnacho,” ten Hag told reporters after the game.
“He did well and I hope he can keep going in this process. He was reliable defending, he worked hard, he was a threat and he scored a goal so I am happy.
“If he can keep this process going, I’m really happy.”
The Dutchman also offered an update on United’s injury concerns ahead of Sunday’s Premier League game with Aston Villa.
“We have some problems in the frontline, with the injuries and illness for Antony, Anthony Martial and Jadon Sancho,” he said.
“But we have also players in the back and more youngsters coming, so I’m happy that we can replace something.
“Lindelof is performing well in combination with Martinez. Sunday he was ill, so not available. Then came Harry, and he did well also.
“Varane, that is an injury, and it hurt us, because (of) also his leadership. But we still have three really good centre-backs, and that’s good and also what we need.
“I’m happy that we have the competition in many more positions. That’s what we need, and also to cover all the games. So I’m happy.”