NEW signing Ben Barba will make his debut at full back in Friday's game against Wigan.

Coach Justin Holbrook confirmed that the former NRL superstar will start at one, with Jonny Lomax switching to stand-off.

Matty Smith will play scrum half in a game that is a must-win with a semi spot at stake.

Saints boss Justin Holbrook said: "Benny will play full back. That is his best position.

"Jonny Lomax will go to five-eighth. He played all of his junior rugby in the halves before moving to full back.

"He wants to get his hands on the ball more. At full back he's tended to run around a lot without getting his hands on the ball.

"The unlucky one is Theo Fages because he's been playing great for us. It is a tough decision and that is what we have done.

"Benny is not just a good runner of the ball, he has the vision of a half.

"He has experience too."