Saints were forced to work hard by a spirited Hull challenge but sometimes lacked the final polish. A double-salvo from two of their best on the night, Paul Wellens and Jamie Lyon, proved enough to win it.
The Saints' coach, Daniel Anderson, said that the players who had missed the game applauded those who won it into the dressing-room. "I like that sort of battle every now and again," he said. "Our defence was absolutely outstanding."
Hull's John Kear, who faces Saints again in a Challenge Cup semi-final in three weeks' time, could not fault his team's effort. "We threw a lot at them, but our execution could have been a bit better," he said.
It has been 17 years since Hull last won at Knowsley Road, although the absence of seven regulars, including the likes of Sean Long and Paul Sculthorpe, from the Saints' line-up must have given the feeling this was their long-awaited chance.
Within the first minute, they had the evidence when Richard Thorne charged down Jon Wilkin's clearance-kick attempt for Richard Whiting to score.
Hull were punished for failing to take their chances when one of Saints' young reserves, Scott Moore, timed a pass perfectly for Mike Bennett to wipe out their lead and go ahead through Lyon's conversion.
Relentless tackling and regular handling errors continued to be the story after the interval but it was Saints who, in the end, made the vital breakthrough.
The 17-year-old Moore showed further evidence of his precocious confidence with a well-judged kick through. Shaun Briscoe had a chance to knock the ball dead but failed to make sufficient contact leaving the outstanding Wellens to touch down just before it could run dead.
Hull attempted an immediate counter-attack but it broke down when Chris Chester knocked on Paul Cooke's pass. Lyon capitalised by picking up the loose ball to run 90 metres for a try, underlining his class in the process.
Hull hit back with a try from Kirk Yeaman which owed everything to wonderful handling from Cooke and Nathan Blacklock.
Briscoe almost set up another but lost the ball trying to get his pass away and then Moore stopped Chester on the line. Hull threatened to the end, but Graeme Horne had the last real chance to swing the game their way when he was stopped a couple of metres short. It was the story of their night.
St Helens: Wellens, Albert, Lyon, Talau, Gardner, Hardman, Moore, Fozzard, Cunningham, Anderson, Edmondson, Bennett, Wilkin. Substitutes used: Mason, Roby, Fa'asavalu, Clough.
Hull: Brisco, Blacklock, Yeaman, Whiting, Tony, Cooke, R Horne, Dowes, Brough, Thackray, Chester, Kearney, McMenemy. Substitutes used: King, Saxton, Carvell, G Horne.
Referee: I Smith (Oldham).
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