Saints put their World Club Challenge misery behind them to maintain their perfect start to their Super League title defence.
Just five days after their 39-0 drubbing by South Sydney, Saints were far from at their best but rode their luck to claim a 21-14 win over a game Castleford outfit still looking for their first win of the season.
The Tigers, who were without stand-off Ben Roberts after he pulled out with a hamstring injury, were their own worst enemies by squandering a host of scoring chances, although Australian winger Justin Carney touched down twice in four minutes to bring them back into the contest after they had trailed 14-0.
Saints demonstrated their clinical finishing after 10 minutes, creating an overlap for left winger Adam Swift to open the scoring and Mark Percival added the goal.
That followed a fumble inside his own 20-metre area by Castleford full-back Jordan Tansey and the visitors were left to rue a number of other handling errors before half-time which cost them any chance of turning their enterprise into points.
The Tigers were unable to take advantage of some powerful running out wide by Junior Moors, while left winger Carney reached the line only to be turned on to his back.
Castleford gave debuts to former London Broncos forwards Mike McMeeken and Matt Cook and the former almost created a try with his first touch, with Tansey pulled back for a forward pass.
Substitute Ryan Boyle was also denied a try for a forward pass and the visitors ought to have made more of a break by skipper Michael Shenton, the former Saints centre.
The misses began to look costly when Saints added a second try three minutes before the break, dangerous full-back Jonny Lomax taking Travis Burns’ short pass to open up the Cas defence and get right winger Tom Makinson over at the corner for his third try in as many league games.
St Helens were forced to switch forward Louie McCarthy-Scarsbrook to the threequarters after Swift limped off after 26 minutes and they continued to perform well below their best.
Trailing 10-0 at half-time, Castleford left themselves with a seemingly hopeless task within two minutes of the re-start when Carney produced a wayward pass after fielding Burns’ kick 10 metres from his own line to present St Helens centre Josh Jones with a simple try.
Nothing, it seemed, would go right for the Daryl Powell’s men, but Carney struck twice in four minutes to blow the game wide open.
Shenton demonstrated his class to get his winger over for the first after Tansey had been brought down short of the line, while scrum-half Luke Gale came up with a perfectly-judged kick to the corner for the second after also making the initial break.
Gale was unable to convert either try to leave his side six points behind and they were unable to take advantage of the extra man when St Helens prop Kyle Amor was sin-binned on the hour for a ‘crusher’ tackle on Tansey.
Indeed, it was 12-man Saints who scored the next try, with Percival taking Jones’ pass and producing a devastating finish at the corner.
He also kicked the goal to make it 20-8 and skipper Jon Wilkin made sure of the win with a drop goal after 73 minutes.
Gallant Castleford continued to play attractive rugby, though, and Tansey scored a consolation try two minutes from the end, touching down Gale’s kick over the Saints defence, and Gale added the goal.