Mark Hughes was left ruing the way Southampton navigated the key moments in the game as his side were well beaten by West Ham at London Stadium.
João Mário opened the scoring with a thunderous finish after 13 minutes, before Marko Arnautovic’s brace left Saints with a mountain to climb at the interval.
Hughes’s men improved after the break, but it proved a tough baptism for the boss in his first Premier League game at the helm.
“We were poor,” he said. “The opening period of a game is vitally important.
“You have to understand as the away team that the home team is going to come flying out of the blocks and you have to be ready to go yourself.
“Unfortunately, as happened against Newcastle, a very similar situation unfolded today.
“We’ve got to stop that trait being a permanent thing because it’s damaging us too critically at the moment.
“Key moments in games are the opening periods and either side of the half-time break. We didn’t navigate those moments well enough and conceded too readily.
“Going in at 3-0, the game was over at that point. We were slightly better in the second half in terms of possession, but never really looked at any stage like we were going to get a foothold in the game.
“We’ve got to be a lot better. The group is honest enough: they’ll look at themselves on an individual basis and collectively, and they need to come in on Monday ready to take things on the chin.”