After conceding 63 goals from 46 Championship games Martin has set his priorities ahead of the new season which sees the club back in the Premier league again.
"We have looked at the defensive side of things a lot. We made a change towards the end of the season which worked really well," he said.
“It will be down to personnel, how we assess it and how we see things, but we do need to be better at that.
“It was difficult coming in last year because when you are trying to play in a certain way you have to prioritise something.
The Saints boss went on to talk about the difficulties of last year and how they can improve.
“So we conceded a lot at the start. Then we went on a brilliant run and had the best defensive run in that period.
“Then we had another wobble where we conceded a lot, but we went back and focused on some key things again and the guys were great.
“There were a few anomalies last season, against Sunderland and Leicester, but we need to make sure that doesn’t happen again.
“That is my job. We need to get better at that for sure. We were the second best in the league for expected goals against but we conceded way too many.
“That was a problem for us. We have been having a look at that all summer. I’ve had many sleepless nights thinking about how to improve the defence.
"But that’s my job, to make sure we work on that. I am confident that we will.”