Man Utd's performance in Europa League loss 'unacceptable': Ten Hag
Youssef En Nesyri scored twice at the Ramon Sanchez-Pizjuan Stadium as Sevilla, 13th in LaLiga, cast aside their domestic struggles to go through 5-2 on aggregate.
United put in a listless and error-strewn performance, with goalkeeper David de Gea and defender Harry Maguire culpable for a couple of Sevilla's goals.
Asked if Sevilla displayed more fight than his side, Ten Hag told reporters: "I have to acknowledge, it's the truth. It's hard, it's tough, but it's the truth."
The Dutch manager said United had to show more desire and more composure on the ball.
"When you get a setback, you have to deal with it, and carry on. It's not about playing skills, it's about character. So be composed and have desire and passion," he added.
"They had more willingness to win. I think that's unacceptable."
United play Brighton & Hove Albion in the FA Cup semi-finals on Sunday before a Premier League trip to Tottenham Hotspur.