Harris takes his men to the Stobart Stadium looking to secure back-to-back wins for the first time this season.
The two sides have met at the Racecourse Ground last month, where a poor start cost Crusaders victory in Wrexham.
Saints to James’, Graham and Roby, ran riot for the away side during a rampant fist half display.
The two players have been in sensational form this year, and Harris had singled them out as the one’s to watch at the Stobart Stadium.
“Last time against St Helens our attitude wasn’t quite right,” Harris said.
“The players understood that and they appreciated that. It is only around a month ago that we last played them and I’m confident that the players will apply themselves a lot better this time around. Hopefully their intensity will be a lot better and the squad will be a lot more focused. We need to stop their threats and also impose ourselves on the game.
“James Roby and James Graham are the two key players for them. They’ve been the constant in their side right the way through the year and they really get the team going forward. They’re world-class players and they are the kind of people other players look to when the chips are down.
“Saints have had to deal with a lot of injuries this year but those two have been fantastic. A lot of the credit has to go to those two players because they’ve kept them ticking over and they’re always consistent. Everybody else has slotted in and around them and they are the biggest threats in my opinion.
“They’ve got a fantastic squad. I’ve looked at the 19-man squad and the likes of Leon Pryce and Chis Flannery are missing. But Saints have still got real quality and they’re getting players back from injury. We need to make sure that our performance is of a high quality.”