Francesco Guidolin admitted Swansea City must do better after they went down 1-0 at Southampton.
The Swans struggled to create chances and were deservedly beaten by Charlie Austin's second-half goal.
Guidolin's men have now lost three of their four Premier League games since they began the new season with victory at Burnley.
And the Italian acknowledged that improvements are required.
"Southampton deserved to win," Guidolin said. "They started very well and they played good football.
"We were prepared to play a good game I thought, but only in the last part of the game when we were 1-0 down did we play a bit better.
"I am disappointed. We have to improve as soon as possible because playing this way, it's hard to win in the Premier League.
"We have to improve in a lot of different situations because if play in this way, it's difficult to win any game in this league."
The early stages of the contest were fairly even, but Southampton carried more attacking menace for large chunks of the game.
The Saints really began to take control as half-time approached, with Virgil van Dijk going close before Nathan Redmond missed two good chances to open the scoring.
The home side continued to press early in the second period, with Kyle Naughton clearing Shane Long's cross-shot off the line before substitute Austin smacked a shot against the bar.
The goal eventually came on 63 minutes, when a Dusan Tadic cross reached Austin at the back post and he drilled home from close range.
The Swans tried to respond late on, with Modou Barrow shooting straight at Fraser Forster before the Saints keeper pushed away Gylfi Sigurdsson's shot.
"I worry about when we will win because that's my job," Guidolin added.
"It's my attitude to always be ready to win if possible. Now we have Manchester City on Wednesday and Saturday and then Liverpool.
"They are more difficult games and for sure we have to improve."
Guidolin changed his team's set-up once again at Southampton, starting with a 4-3-2-1 formation.
He then switched tactics twice in the second period, first when Jefferson Montero came on for Ki Sung-Yueng and then when debutant Borja replaced Jack Cork.
"After the game it's easy to say this line-up is not good, another line-up is better," he said.
"We started here like we played in the second half against Chelsea. After that I changed it again because we didn't play well.
"But this is not the problem for me. I think I know some problems, but I have to speak with my players and with my assistants about them."