Wigan duly collected their League Leaders' Shield after this typically rumbustious derby, but only after they had their party spoilt by their neighbours and by the dismissal of Michael McIlorum.
Saints, beaten twice by Wigan this season, took advantage of playing against 12 men for three-quarters of the match after the hooker was dismissed for a high tackle.
Their victory, for which they still had to work hard against depleted opponents, means that they are all but mathematically certain to be at Warrington in the first round of the play-offs next weekend.
With these two sides both involved in the play-offs next weekend, there was always the risk of this fixture being something of a phoney war.
For one man, however, it was in deadly earnest. Stuart Fielden was playing only his second match in two seasons. The prop forward was trying to seize a belated chance to show that, despite his horror run of injuries, he still has plenty to offer. Elsewhere, in the team selections, both coaches resisted any temptation to rest key players.
Wigan had some dodgy early moments, notably when Anthony Laffranchi lost the ball on the try-line when he might have forced his way over, and when Sam Tomkins failed to mop up Jon Wilkin's low kick. But then it was another returnee, although not one absent for as long as Fielden, who seemed to have got the Warriors on course.
Thomas Leuluai was starting for the first time since breaking his leg at the start of June. After 12 minutes, he scored a try of extreme simplicity, taking a pass from Brett Finch at dummy-half, selling a hint of a dummy and strolling over.
It should have been the start of the Warriors settling to their task, but four minutes later they were down to 12 men, when McIlorum was sent off for a late, high tackle on Laffranchi. The referee, James Child, consulted with his touch judge and then had no hesitation in showing the hooker a red card.
McIlorum does not have the best of records so, subject to next week's disciplinary hearing, his play-off series could be over before it has begun.
Wigan felt his absence as errors allowed Saints to dominate the rest of the first half. The first really damaging one was when Finch was pulled up for a forward pass to Gareth Hock.
From that possession, Tony Puletua attacked the line and managed to get his pass out of the tackle for James Roby to score.
The next crucial blunder was when George Carmont and Pat Richards got in a tangle under a high kick. This time Saints moved the ball wide for Tom Makinson to touch down and add his second conversion.
A try from an equally expansive attack and an equally good conversion, both from Richards, brought Wigan level at the start of the second half. Another surging run from Puletua regained the lead for Saints, with Andrew Dixon this time finishing off the move.
Both sides had their chances after that, but the first to take one was Saints' young centre, Josh Jones, as the Wigan defence was at last over-stretched. Jonny Lomax, a couple of minutes later, took further toll on exhausted opponents, although Tomkins pulled one back in the final minute.
Wigan Tomkins; Charnley, Goulding, Carmont, Richards; Finch, Leuluai; Fielden, McIlorum, Lima, Hansen, Hock, O'Loughlin. Substitutes used Mossop, Farrell, Dudson, Flower.
St Helens Wellens; Makinson, Shenton, Jones, Meli; Hohaia, Lomax; Perry, Roby, Laffranchi, Flanagan, Puletua, Wilkin. Substitutes used McCarthy-Scarsbrook, Greenwood, Clough, Dixon.
Referee J Child (Dewsbury).