Both sides were depleted by injuries before the game really took hold, as Wigan lost Liam Farrell in the warm-up, while Curtis Sironen lasted just nine minutes for St Helens.
Marshall raced in for his 22nd Super League try of the season, courtesy of Adam Keighran’s foresight in seeing him on the wing, with his clever pass sending him through to slice open the Saints defence.
Even more impressive was Farrimond’s score minutes later, which came from a clever kick and chase and sent the Cherry and Whites 12-0 up.
Following the break, Wigan almost scored their third try as Zach Eckersley touched down, but it was waved away as replays showed Miski knocked on the build-up.
The game opened up for Saints after Ellis saw yellow, and they should have got on the board when Harry Robertson made an inspired run and offloaded to Matt Whitley, who was thwarted by a try-saving tackle from Jai Field.
With St Helens failing to make their advantage count, Wigan could have wrapped up the win in style as Marshall touched down again, but his efforts were chalked off because of a forward pass in the build-up.
Wigan eventually scored their third after a sustained spell of pressure as Walters crossed for his first try for the club, following Miski’s impressive kick from the wing which ripped open St Helens once more.
It was a chastening afternoon’s work for Saints, who face another in-form side in Hull KR in their next Super League meeting, while Wigan face their cross-city rivals Hull FC off the back of their heavy defeat by struggling London Broncos.
