Danny Orr had the sort of game that underlined how difficult he will be to replace at Castleford, but it was not enough to make up for their battling failings.
Orr, who has rejected a new contract and will decide between offers from Wigan and Hull at the weekend, scored three tries and set up another in one of his best displays of the season, but it was Castleford's collective frailties in defence that decided last night's match.
A few boos greeted the reading of Orr's name before the game, with the whole evening threatening to be a test of his ability to put the question of his future out of his mind.
His first contribution was a positive one with a neat pass to Francis Maloney that led indirectly to a penalty for holding down. Orr kicked that and was booed again, although mainly by St Helens fans.
That lead lasted only until Saints began to exert some sustained pressure, with Sean Long skipping away from the defence and Mick Higham scoring from his inside pass. It was Orr who restored Castleford's advantage, taking Ryan Hudson's pass on the last tackle of a set before plunging over for a try, which he also converted.
Again Saints came back quickly, Darren Britt's short pass to Darren Smith opening up the Castleford defence for Paul Wellens to score, with Long adding his second goal.
Up popped Orr again, after Hudson had charged down a kick from Paul Sculthorpe, racing through from just on side for an opportunist try.
The same pattern was repeated, however, as Saints hit back immediately, more weak tackling allowing Sculthorpe to set up Wellens. This time, Saints consolidated their advantage, Britt again getting the crucial ball away and Martin Gleeson charging in.
Castleford badly needed the first score of the second-half, but it went to Saints when Michael Eagar knocked on, Higham raced away with the loose ball and Darren Albert supported to score. Sculthorpe and Albert then combined to give Gleeson his second.
Mitch Healey's pass to Tom Saxton produced a retort from the Tigers, before another brilliant piece of play from Orr sent Michael Smith in to cut a margin back to 10 points.
Healey and Hudson both went close to the try that would have put Castleford right back in it, but Keiron Cunningham's first - and overhead - pass to Higham ended that possibility before Long intercepted from Healey for a try to go with his seven goals.
Just after Orr was made Castleford's man of the match, he exchanged passes with Eagar for his hat-trick. He had shown his commitment; the same cannot be said of some of his team-mates' battlings.
Castleford: Saxton; Rogers, Mellor, Maloney, Pryce; Orr, Healey; Sykes, Hepworth, M Smith, Johnson, Fritz, Hudson. Substitutes used: Eagar, Thackray, Harland, Godwin.
St Helens: Wellens; Albert, Gleeson, Hooper, Stewart; Long, Higham; Britt, Cunningham, Mason, Bennett, D Smith, Sculthorpe. Substitutes used: Kirkpatrick, Edmondson, Joynt, Jonkers.
Referee: R Silverwood, Mirfield.