Claude Puel said he had to protect a number of his players for the Emirates FA Cup clash with Arsenal.
Saints were beaten 5-0 at home by the Gunners, with the manager making ten changes from the side that triumphed against Liverpool in the second leg of the EFL Cup semi-final.
Puel said he had to make such sweeping alterations due to a lengthy injury list and the fact they have two big Premier League games coming up this week, against Swansea and West Ham United.
“We have a lot of injured players and I tried to protect all the players who are important for the next games,” said Puel.
“Before the game, we had nine players not available. Other players have been playing every three days, and it's not possible for us to play the same team every three days against a great team. They can recover, because they didn't play.
“I am responsible, of course, for this defeat. For me, it was important to protect some players and to keep good chances for the next game, and to protect against injuries also.
"Of course, it was important for us to recover, because we have got to have two strong games in the Premier League – very important games for us, and it's important to give a good answer and prepare for the next game.”