Mauricio Pellegrino says every week between now and the start of the season is crucial, following a positive training camp in Austria.
The new manager spent the best part of a week away with his players, culminating in Saturday's 0-0 friendly draw with St Gallen.
The squad has now returned to Southampton, and they will report back to Staplewood on Monday, ahead of flying out to France seven days later for another camp.
Pellegrino said the visit to Austria, which ended with a short trip across the Swiss border to meet St Gallen, was an important one.
"Not just on the pitch, it's about our style of training sessions and just to see how the players react," he said.
"Every week for us is crucial, because we don't have too much time. We will play another four games, which is not too much, but we have to try to do our best every single day.
"We are expecting the other players that will arrive next week and hopefully it will be better for us."