Saints have announced the signings of Shannon McDonnell until the end of the season and Tongan international Atelea Vea.
Aussie McDonnell, 26, has joined as a free agent and will provide competition at full-back following Jonny Lomax’s season-ending injury.
The ex-Hull FC player told how he was grateful for a second chance in Super League.
He said: “I’m pleased to be part of this club. It has great traditions, coaching staff and players and this is a good opportunity for me to come and play rugby league again.
“I am keen to get training and playing and I will get my head down and take each game as it comes.
“I like to play off the cuff and be consistent in both defence and attack. I am a full back but I will stick my hand up to play wherever the coach wants me to.”
Predominantly a full back, McDonnell previously played for Wests Tigers and Newcastle Knights in the NRL.
He represented New South Wales at Under 19s and was an Australian Junior Kangaroo.
In 2011, he moved to Hull KR and two years later joined their rivals at the KC Stadium.
As well as making more than 100 career appearances, he played for the Exiles in 2012.
“Shannon is a great addition for us,” said Saints head coach Nathan Brown. “He has a lot of experience in his position and will add strength and depth to our squad.
“Losing Jonny Lomax for the rest of the year has seen Paul Wellens move back to a position he has played in for most of his career.