Saints are now all but assured of a Betfred Super League Semi Final following a 30-4 win over Salford Red Devils.
Alex Walmsley grabbed a brace whilst Mark Percival tallied 14 points in a victory that takes Justin Holbrook’s men into third.
But they were pushed all the way by a Salford side that ended the game with 12 men after Ryan Lannon’s rash challenge on Theo Fages in the first half.
Up until that moment the Devils had been a real thorn in Saints’ playoff hopes.
Within the first couple of minutes Tommy Makinson had produced an important tackle on Manu Vatuvei to stop a certain try.
But on the very next set, Niall Evalds profited from a sweeping move.
Saints almost replied immediately through Jon Wilkin and James Roby but had to wait until around the 15th minute to finally get on the board.
Fages found Ben Barba on the left hand side, and the fullback unlocked the defence to put Percival over.
The game was end to end, and physical too, with Salford shading the main scoring chances.
They had one chalked off for a Vatuvei knock on in the build up on the half hour mark – but three minutes later Saints took the lead.
Barba did the damage once again, getting Saints into great field position before Roby found Walmsley on the burst for his 10th of the season.
Saints were buoyed and gained a further numerical advantage when Lannon was sent off for a late and high hit on Fages after he had kicked the ball.
Salford were incensed at the decision as on the tackle previous, Jordan Walne had left the field following a forearm from Walmsley as the big prop charged up the ball.
Percival knocked over a penalty to calm it down and take it out to 12-4 – but missed another shot at the end of the half after Junior Sa’u had gone in high on Barba – and then hit him on the floor.
Salford came out in the second half throwing big hits on Saints’ charges – and it worked as they rattled the visitors and forced a number of errors.
But Saints steadied the ship, going close on 48 minutes through LMS before Regan Grace polished off a fine move involving Matty Smith, Barba and Percival; only for it to be called back as the winger had his foot in touch.
Saints did finally cross and take the game away from Salford with 15 minutes to go.
After shunning the opportunity to take a simple penalty in front of the sticks, a lovely short ball from Fages saw Zeb Taia increase the lead.
Walmsley then crossed for his second after Smith’s short pass.
The double underlined Saints’ dominance in the second half and that was further cemented when, at the death, Barba sidestepped and handed off a would be tackler to dance his way under the posts.
Goals: O’Brien (0 from 1)
Tries: Percival, Walmsley (2), Taia, Barba
Goals: Percival (5 from 7)
REF: J Child
5. Niall Evalds; 24. Jake Bibby, 22. Kris Welham, 4. Junior Sa’u, 31. Manu Vatuvei; 6. Robert Lui, 1. Gareth O’Brien; 26. Daniel Murray, 9. Logan Tomkins, 12. Weller Hauraki, 11. Ben Murdoch-Masila, 3. Josh Jones, 32. Tyrone McCarthy.
Subs: 8. Craig Kopczak, 15. Ryan Lannon, 18. Jordan Walne, 20. Kris Brinning.
37. Ben Barba; 2. Tommy Makinson, 3. Ryan Morgan, 4. Mark Percival, 28. Regan Grace; 6. Theo Fages, 24. Danny Richardson; 14. Luke Douglas, 9. James Roby, 16. Luke Thompson, 36. Zeb Taia, 20. Morgan Knowles, 12. Jon Wilkin.
Subs: 7. Matty Smith, 8. Alex Walmsley, 13. Louie McCarthy-Scarsbrook, 18. Dominique Peyroux.