Jackie McNamara says his Dundee United side were physically dominated by Hamilton Academical in Saturday's 4-0 drubbing at New Douglas Park.
United seldom threatened the Accies goal, finding themselves trailing 3-0 at half-time.
"I'm very angry, frustrated, that's probably the worst half we've had under my watch," McNamara told BBC Scotland.
"They bullied us; we gifted them a few goals as well. We made things hard for ourselves."
United have won just one of their opening four matches in the Premiership.
"It's a learning curve for all of us - in every game, whether good or bad, you have to earn the right to play football," continued McNamara.
"If it's a battle to start with, I said to the players, no matter if it's 30 minutes, 40 minutes to get the ball down and play, you have to match the opposition first and foremost, and the first half we didn't do that.
"They were on top of us, they had more energy, maybe not having the game midweek. The hunger was there, you could see they were fighting for everything."
Accies player-manager Martin Canning remained level-headed after his side secured both their maiden goals and victory of the campaign.
"I thought all over a park, to a man, they won their battles all over the pitch," said Canning.
"Our players worked their socks off and earned the right to go and dominate the game. I think the biggest thing today was our intensity, our ability to go and work.
"I've always said we won't get too high when we win and we won't get too low when we lose. It's just trying to be as steady and consistent as we can."