Ronald Koeman was left disappointed following Southampton’s 2-1 defeat to Sunderland at the Stadium of Light.
The Saints boss was unable to understand why his side had played their best football once they had gone down to ten men following James Ward-Prowse’s red card.
Two successful penalties from Jordi Gomez was enough to win the game for the hosts, with Sadio Mané’s goal proving just a consolation for Koeman’s men.
Speaking to youtube.com/southamptonfc, Koeman said: “I am frustrated and disappointed and I am asking myself and I asked the players why we can play football with one player less on the pitch and why we don’t do that before.
“I think the first hour was not good, but we were a little bit lucky with the equaliser after the 1-0.
“But the first ten minutes of the second half was very poor. We were very poor in our ball possession and out of that situation came the 2-1 and the red card.
“After that we played football, we had some good chances to score but that’s strange. Sometimes you don’t understand why you can play football, good football ten against 11 and it’s not possible when it’s 11 versus 11.
“When I show the video about the first ten minutes after half-time, that will be enough for the players to know.”
The reaction to going a goal down, and the dominance his side showed when they went down to ten men, pleased Koeman, but overall he felt it was not enough.
“Maybe unlucky but you can say it’s too late,” he added. “You have to start like that and that makes it easier.
“They are fighting not to go down, they put in everything and it’s strange because we showed physically that we are more fresh against 11 with ten.
“If you draw with ten men on the pitch that’s a good result.
“We have to recover quickly from this, we have to think about why and we have to make things better next time.”