Claudio Ranieri says he should have rotated his squad to keep them fresh, admitting Southampton should have beaten Leicester on Sunday.
The visitors, who made seven changes to the side who drew against Hapoel Beer Sheva in Israel in the Europa League on Thursday, had the better of the goalless draw at King Power Stadium.
"I recognise they played better than us and deserved to win," Ranieri said. (Kasper) Schmeichel made two or three great saves and they hit the post.
"For us it is ok, one point and a clean-sheet. Now I have to think about when we play every three days.
"Maybe it was much better to give some rest to some players. I changed just one player. It is not enough.
"It could be the schedule. Maybe we ran more than other matches because it was difficult to stop them."
A number of Ranieri's squad now head off to play for their countries over the next two weeks with the Italian aware his rotation plan will face a stern test when Leicester return to action.
They have a busy week featuring a trip to Chelsea, a European clash with Copenhagen and finishing at home to Crystal Palace.
"How many players stay with me now, six? seven? The rest go for international matches," Ranieri added.
"Then they come back a few days before Chelsea and we have a Champions League game after that. I have to think hard."