THREE costly errors came back to bite Wigan as the chance of registering a derby double slipped from their grasp.
Trailing 16-14, the game was on a knife edge when Matty Bowen allowed a regulation high-ball drop through his fingertips, and opposite No.1 Shannon McDonnell dribbled the ball over the line to score.
Bowen - only back in the side for the past three games - had earlier failed to deal with a kick which presented Saints with another of their five tries.
And those mistakes were compounded when Dan Sarginson, bringing the ball back from his own half, threw a wild pass which was snatched up by Jon Wilkin to push the scoreline out to 28-14, and end any hopes of a Wigan fightback.
Those three flashpoints aside, this was a derby which was at times pulsating and often niggly.
Cyling hero Sir Bradley Wiggins watched on from the stands but the club of which he is a lifetime member were, ultimately, second-best.
George Williams had his moments, Micky McIlorum was typically aggressive and Joe Burgess pressed his England claims with a scorching opening half-try, but Wigan rarely matched the home side’s cohesion and verve.
The stakes were already high, but after Leeds lost 31-24 to Castleford the night before, these two sides went into the contest knowing they had a golden chance to take a giant stride at the Super League summit.
Dom Crosby replaced Ryan Sutton in the only change to the Warriors side which beat Huddersfield 32-18 five days earlier. Hooker James Roby - an injury-doubt during the week - took his place in a Saints front-row which Wane had targeted as being the crucial battle-ground in deciding the outcome.
Predictably, the home fans booed Ben Flower’s name as it was read out in the team line-ups - this was his first meeting with Saints since being sent off in the Grand Final for punching Lance Hohaia.
There was little to split the sides by half-time, with each team scoring two tries - efforts by Sarginson and Burgess bookended by touchdowns by Adam Swift and Jordan Turner.
Saints, though, started the second-half the brighter and retook the lead in the 45th minute. Wilkin dribbled a kick through which Bowen failed to deal with, and Burns was on hand to pounce. Percival’s goal made it 14-10.
Full-back Bowen produced a sweet tip-in to Joel Tomkins, who angled over to lock the scores.
The seesawing exchanges continued, and with 25 minutes to go, Saints elected to kick a goal when Liam Farrell was penalised for a flop.
Wilkin took running repairs on a head-gash, which replays suggested was caused by McIlorum’s knee - dialing up the volume of the exchanges among the fans. He had the last laugh with the try which sealed the win, but only after Bowen’s second spill had gift-wrapped McDonnell a try, with Percival added a late penalty to eat up the clock. If Flower started the game as the pantomime villain among the home fans, the tag had been passed to Bowen by the end.
St Helens: McDonnell; Dawson, Percival, Turner, Swift; Burns, Wilkin; Amor, Roby, Walmsley, McCarthy-Scarsbrook, Flanagan, Jones. Subs: Masoe, Richards, Savelio, Fleming.
Wigan: Bowen; Charnley, J Tomkins, Sarginson, Burgess; Williams, Smith; Mossop, McIlorum, Flower, Bateman, Farrell, O’Loughlin. Subs: Crosby, Powell, Tautai, Patrick.
Referee: Richard Silverwood
Starman: Micky McIlorum