The 36-year-old has been a mainstay in the Saints side that rose from npower League One to the top flight but was dropped four matches into the season, having conceded 14 goals.
"When you are used to playing week in, week out, which I have been certainly at this club over the past three or four seasons, it is always difficult," he told the Daily Echo.
"But I accept that you can't always have it your own way and that the right thing to do is to keep your head down and work as hard as you can.
"Obviously I looked at myself and what I was doing. I felt that in terms of where I was, I am 36, it is about maintenance and staying on top of yourself physically.
"I felt that if I stayed in good shape and carried on doing what I was doing my time would come again.
"It is not my decision, it is a decision the manager takes."