The irresistible force and the unmovable object will collide head-on in a few days' time and at stake is a place in the Old Trafford Grand Final next month.
Both clubs are in a rich vein of form - St Helens unbeaten in their last half dozen Super League fixtures and deadly rivals Wigan Warriors having won 12 of their last 13 matches.
Something has to give with the only consolation being that the losers will get a second bite of the cherry.
But respective coaches Justin Holbrook and Adrian Lam will want to get the job done and dusted at the first time of asking - and the stage seems set for an explosive derby at the Totally Wicked Stadium on Friday.
Saints have held all the aces so far this year, having beaten their neighbours three times and boasting a 100 per cent home record in 2019 but that won't worry battle hardened Wigan.
They may not be eye-catching at times but know how to grind out a win - a formula which has proved successful in the recent past.
"It's potentially the biggest derby in Rugby League,'' claimed Wigan head coach Lam who insisted: ''These are the kind of games you want to play in.''
He added: "Saints have been the best team in the competition all year and they will be red hot favourites, but we will go there with a team we think can challenge them."
On the other hand, Holbrook will be hoping to add to the League Leaders' Shield, which is already in the club's hands, and it would be the icing on the cake for the Aussie before he heads home to take over the coaching reins of Gold Coast Titans in the NRL.
He said: ''I've loved my time at St Helens and it would be a fitting finale as far as I'm concerned if I could lead the team to victory at Old Trafford for the sake of everybody connected to the club."