Wigan Warriors 2 St Helens 26: Hosts try-less in another derby loss
Any loss to their arch-rivals is painful, but their failure to carve out anything resembling an attack on Saints' line during the entire 80 minutes made this one particularly difficult to stomach.
John Bateman was sinbinned in either half and Willie Isa also shown yellow for losing his head; frustration was finger-printed all over their display.
Saints were deserved winners, no doubt, without being outstanding; they just had the greater composure, slicker combinations and had some notable displays led by teenage halfback Lewis Dodd.
Their win follows victory at the Totally Wicked, registering a double against Lam's side and taking the coach's record against Saints to played nine, won one.
This year, while they remain seated in the play-offs positions in fourth, their failure to beat any of the other sides in the top-five has hosed down expectations of reaching a second successive Grand Final.
Long, snaking queues two hours before kick-off illustrated the appetite for the derby from both sets of supporters, and as kick-off approached the atmosphere was crackling.
The absence of Sam Powell (head injury) and Jai Field to a knock saw Lam start with Joe Shorrocks at No.9, who motored through a tireless defensive stint before making way for Amir Bourouh before the break.
Liam Marshall was injured in the first carry, forcing him off the field for a spell. During his absence, Saints went ahead, Regan Grace firing through on a piercing break from inside his own half and finishing later in the set.
It was a rare clear chance for either side, but the physical exchanges had plenty of niggle - not least when John Bentley poked Bateman with his boot, the Wigan player reacted and both were, perhaps harshly, dispatched to the sinbin.
Wigan exerted plenty of energy but rarely troubled Saints' line and one rare trip into enemy territory, captain Liam Farrell elected to kick a penalty, Harry Smith cutting the margin to 6-2.
But Saints quickly extended their advantage when Dodd ripped the ball from Ollie Partington's grasp close to the line to scoot over. Lachlan Coote struck both conversions to make it 12-2 at half-time.
When Bentley and Bateman returned, the Saints man set his rival sprawling with a powerful fend.
Errors crept into both displays before the break with neither side threatening anything like a further score, but it was Saints who rediscovered their composure quicker from the restart. Dodd's weighted kick was chased by Coote who was collared and dragged down by Hastings, but Dodd struck the subsequent penalty to open up a 12-point gap.
As the clock ticked on, frustration was finger-printed all over Wigan's display. Bateman was sinbinned again - this time for dissent - and soon after his return, Isa followed. In truth, he should have gone earlier for an off-the-ball challenge which went unpunished.
Mark Percival extended the visitors' lead with a smart try and the damage would have been greater had Coote not missed the conversion and an earlier penalty. With the game entering the final 10 minutes, Coote added a penalty to poke them 20-2 in front and Alex Walmsley added the crowning glory.
Wigan: Hardaker; Bibby, Isa, Gildart, Marshall; Smith, Hastings; Partington, Shorrocks, Havard, Pearce-Paul, Farrell, Smithies. Subs: Bateman, Bourouh, Bullock, Byrne.
St Helens: Coote; Naiqama, Welsby, Percival, Grace; Lomax, Dodd; Walmsley, Roby, Lees, Thompson, Bentley, Knowles. Subs: McCarthy-Scarsbrook, Paasi, Smith, Batchelor.
Referee: Chris Kendall