Manchester United lost 4-3 to Copenhagen, in a Champions League clash on Wednesday night.
It was a game marred by VAR controversy, as Marcus Rashford was sent off in first-half, with United leading 2-0.
For Ten Hag, VAR and poor officiating ruined the game.
Speaking to TNT Sports, Erik ten Hag said: “I think we played very good until the red card. The red card changed everything. Then it becomes a different game. We concede two goals that shouldn’t count.
“It is disappointing. Not only tonight. We had so many decisions against us in other games. That’s how it is. But the season is long. At one point it will turn in our favour. It is harsh decision. Marcus Rashford was going for the ball.
“The review was over, then the referee went up to the screen. After half-time it was better but the two goals should not count. The first is offside, there is a player in front of Onana. The second, what can you do about that?”