Sam Tomkins says the momentum of Saints' win over Salford last week will give them the edge over Leeds when the two teams meet on Thursday night, live on Sky Sports 1 from 7pm.
Matty Smith's perfectly struck kick from 40 metres completed the most remarkable of comebacks from Justin Holbrook's side last week, who had looked dead and buried with seven minutes remaining as they trailed 24-8 before coming away with a 25-24 win.
Wigan full-back Tomkins, who will be our studio guest for Thursday's game, believes Saints will be flying high from the win, and says that will be the difference at Headingley.
"Saints will be coming into this with a lot of confidence," said the England international.
"Looking at the game last week against Salford, they were 16 points down and came back to win it with a drop goal.
"Games like that give you massive confidence because it means not only can you grind out a win, but you can come from behind and find a way to win - the best teams do that."
Tomkins believes Leeds will be eager to prove they have learned from their 2016 season, but still feels Saints will have too much for Thursday's hosts, who are missing Jamie Jones-Buchanan and Danny McGuire through suspension.
"Going off last year, how disappointed they were not to make the top eight, they'll be making sure of it this time around," said Tomkins of the Rhinos. "They're sitting strong near the top, and they look in good shape.
"They will miss Danny McGuire and Jamie Jones-Buchanan. In these big games, you want experienced players, and those two are probably the two most experienced that Leeds have got.
"Leeds still look good, but Saints will go into this more confident than Leeds off the back of last week.
"Saints have got nothing to lose, they're playing a team above them off the back of a great win - they'll throw everything at Leeds.
"That said Leeds are no slouches, and Headingley is a very tough place to win. There is a certain atmosphere and feeling when you get there; it's a tough place to get two points from."
Tomkins says that experience counts for more during the latter part of the season, but says neither of Thursday's team holds a particular advantage in that area.
"Both these side have played for and won trophies, and once you know how to win big games you can always fall back on that experience - both clubs are synonymous with winning trophies so they know how to win big games."
One of the key players for the visitors, says Tomkins, will be the man who won it for them last week.
"Matty Smith will be running the show for St Helens. Matty is a leader, he leads from the front and bosses everyone around him and I think that will be vital.
"They will need to get into a real arm wrestle with Leeds, because the Rhinos have a lot of strike runners like Joel Moon and Kallum Watkins, so they can run away with games quite quickly.
"Matty will have to make sure St Helens set the tempo and force Leeds into an arm wrestle - I think his kicking will be a big component on the day."
Tomkins is looking forward to the battle between the two hookers.
"James Roby is one of the best hookers in the country - if not the best.
"Matt Parcell has been one of the best signings of the year, he's come in and given them a huge spark, but he's relatively inexperienced in Super League, while James Roby has been one of the best hookers in Super League over the last ten years. So that's going to be a very interesting battle."
The Warrior says St Helens will need to keep Leeds quiet in the early stages of the game to reduce Parcell's ability to run riot later on.
"Leeds tend to get on a bit of a roll, and then let him run around and do his thing, causing havoc through the middle.
"Saints will have to make sure they get on top of that battle and limit the impact of Parcell."
"I think it's going to be a brilliant game.
"There are plenty of players on either side who are capable of scoring great tries. Joel Moon and Kallum Watkins are probably Leeds' two most dangerous threats, and they are up against Mark Percival who wants to fight Kallum for that England jersey - so it will be a good battle."
Watch Leeds v St Helens live on Sky Sports 1 from 7pm on Thursday