Saints also announced a coaching change this week, with Kevin Walters due to join from next season.
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Jackson Hastings was sent off for punching Tyler Dupree, then clashes continued off the pitch between St Helens and Castleford Tigers
The Australian's new side took an early lead, and tries from Jack Welsby, Shane Wright, Jacob Douglas, Tom Humphreys and Tristan Sailor made it 30-0 before the break.
Captain Jackson Hastings had added five goals, but lost his cool and was sent off after an altercation with Tyler Dupree for violent conduct.
Dupree was sin-binned for the same incident, and tempers continued to flare as the teams disappeared down the tunnel for the break.
Nene McDonald added a sixth try for the hosts after the break, making a Castleford comeback look increasingly unlikely.
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Louis Senior and Laulu-Togaga'e finally got them on the board, before Saints finished the game with 10 men after Alex Walmsley and Chris Matagi were both sent to the sin bin.
St Helens interim boss Eamon O'Carroll told BBC Radio Merseyside: "I said I wanted to see the attitude of the players, and what better way to display that than when you go down to 10 men for 45 minutes?
"The players were fantastic. We simplified a few things, which probably helped, because everyone knew what the role was and their position."
Commenting on Hastings' dismissal, Castleford director of rugby Chris Chester told Sky Sports: "Scott Murrell just jumped (in the way of Dupree). We all know the rules, you can't punch people in the face.
"We'll let the disciplinary (match review panel) deal with those kinds of things. That's what they're there for."
Hull KR slump to another home defeat
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Highlights of the Super League clash between Hull KR and Toulouse Olympique
Hull KR slumped to a second home defeat of the week as Toulouse ran out deserved 32-12 winners following a ruthless second half at Craven Park.
The Robins were beaten at home by play-off rivals Warrington on Tuesday night, and head coach Willie Peters dropped both Tevita Pangai Junior and Mikey Lewis following their upcoming bans which were handed out in the wake of the 34-28 defeat against the Wolves.
It was a scrappy start - much to the frustration of the expectant Hull KR fans - as Toulouse dug in during the opening 20 minutes and then exerted some control before Mathieu Jussaume scored the opening try on the half-hour when he broke through down the right.
The defending champions, chasing a home play-off berth, finally sparked into life when substitute Elliot Minchella went over in the 35th minute after a surging run by Peta Hiku, with Rhyse Martin adding the extras to make it 6-6 heading into half-time.
Toulouse opted to kick for a penalty early in the second half after a late tackle from Tom Amone, but Cesar Rouge saw his 35-metre attempt bounce off the crossbar.
Hull KR continued to be pushed back and Toulouse deservedly did get themselves in front again after 57 minutes when Benjamin Laguerre burst down the left and fed Romeo Tropis to go on to touch down under the sticks.
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Toulouse further extended their advantage when Anthony Marion got on the end of a kick through and barged over, with the try given following a lengthy video review which showed the ball had been grounded after Hull KR initially had looked to have held him up.
Hull KR, who face leaders Wigan next week, crumbled again when Paul Ulberg was played into space down the left corner after 65 minutes before Tropis burst clear through down the other channel. Luke Polselli added another late scrappy Toulouse try after a kick bounced off the post and Louix Gorman got a consolation score for the home side in the closing stages with a fast break down the left.
Arthur's late drop goal seals Hull fightback
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Highlights of the Super League clash between Catalans Dragons and Hull FC
Hull half-back Jake Arthur landed a late drop goal to seal his side's thrilling fightback as they beat Catalans Dragons 27-26 at the Gilbert Brutus Stadium.
Arthur coolly slotted over a match-winning one-pointer with six minutes left to clinch Hull victory over former boss John Cartwright's Catalans and just their second win in 10 Super League games.
Hull trailed 26-14 early in the second half, but came storming back through converted tries from Harvie Hill and Aidan Sezer to tie the scores before Arthur's match-winning effort.
The visitors led through early tries from Logan Moy and Lewis Martin and led 14-12 at half-time after Catalans had hit back through touchdowns from Charlie Staines and Kruise Leeming.
Catalans appeared to take control of the match when Edenn Rogers-Smith and Leo Darrelatour both went over early in the second period, either side of Guillermo Aispuro-Bichet's penalty, to put them 26-14 ahead.
But Hull launched their fightback as Hill and Sezer both went over for converted scores in the space of six minutes and Arthur had the final word.
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Hull have climbed up one place to 11th in the table, while Catalans sit ninth after their 15th defeat of the season.
Hull interim head coach Andy Last said: "It was a nail-biting game, it went right down to the wire. I'm just really proud of the playing group.
"I spoke all week about showing our personality and our performance when it gets tough and to make sure you answer those questions with your effort and your actions."
Sky Sports will show every game of the Super League live this season, including two matches each round exclusively live. The remaining five matches will be broadcast on Sky Sports+. %!s()