Ronald Koeman feels Southampton deserved better than a 3-2 loss in Sunday's Premier League encounter with Manchester United.
The home side dominated proceedings early on and deservedly went ahead via Graziano Pelle.
Nevertheless, an Anthony Martial double and a Juan Mata strike then put the game out of Southampton's reach, with Pelle's second goal in the closing stages of the game not enough to salvage a draw.
"I am disappointed because in my opinion we beat ourselves here," Koeman said at the press conference.
"The first 30 minutes were perfect in how we like to play and how we like to test our opponents. It was a great team performance, but details make the difference.
"We were unlucky on their first goal. I hear it was offside, but that's what happens. Last year Jose [Fonte] made a mistake passing it back to the goalkeeper and this year it was Maya [Yoshida].
"But then United were the much better team after that goal. In the last 15 minutes we got close, but two great saves from David de Gea denied us."
A sloppy backpass from Fonte resulted in United's second goal and Koeman was not impressed with the experienced centre-back's action.
"I hate players who always play the ball back to the goalkeeper. Always the ball forward, because then you put the pressure on them. I always tell them not to play it back to the goalkeeper, but tomorrow I will have to tell them again. We have to learn from that, we did it last year and we did it today again. We beat ourselves.
"We defended well, but after the 2-1 we lost belief and we lost control. That was United's best period of the game."
"I think we were very strong going forward as well, because every attack was dangerous. I thought Sadio Mane and Pelle were very good today."
Like Pelle, Martial also got two goals and Koeman was full of praise for the young Manchester United striker.
"It's difficult to stop him. I think he's strong and fast, but when you pay that kind of money you expect that..."
