The Finnish goalkeeper has been inspirational since arriving from Scottish Premier outfit Hearts at the start of last season.
Saints finished eighth last term thanks in main to a solid defence and James Beattie's goals.
Goalkeeping coach Hans says Niemi has to be seen as the cornerstone of a defence that conceded just 16 goals at St Mary's last season and only 11 at home so far this time around.
"Not that many people knew about him when he moved from Hearts," said Hans. "He went to Southampton for quite a lot of money, they made quite an investment in him but when you look at what he's done for them, he's repaid it.
"I think he's performed miracles for them. Week in, week out you can see him making saves out of this world and that's one of the reasons why Southampton have pushed on from recent seasons.
"I always include a goalkeeper in a back four. When you look at at goals conceded in recent seasons, Southampton have been very consistent and very solid. A big part of that is the goalkeeper.
"As I've said before, every goalkeeper in the Premier League must be a good shot stopper. You expect that.
"But it's the match-winning saves, the crucial moments that when you look at it, you are thinking 'that's a goal' but somehow he gets a hand to it.
"He's also an outstanding kicker, his distribution is good and strong from goal kicking. For me, he's one of the best in the Premier League."
Hans Segers reckons Antti Niemi has to take a slice of the credit for the turn around in Southampton's fortunes.