Josh Griffin sent off for Hull FC
Saints last lifted cup in 2021 and have won past four Super League titles
FT: Hull KR 28-10 Salford - Robins first team into semis
Wigan v Warrington & York v Leigh in other quarter-finals on Sunday
Lewis Dodd, goal Joey Lussick
Davy Litten runs towards halfway and offloads to Liam Sutcliffe, who then knocks on.
Then St Helens' Tee Ritson races through from deep inside the Hull half and is eventually tackled, but Lewis Dodd runs in soon after.
St Helens are in control, now. It's difficult to see how Hull can come back from this.
Joey Lussick kicks the two.
Image source, PA MediaHull FC 12-18 St Helens
Alan Hunte
Ex-Great Britain winger on BBC Radio Humberside
Hull aren’t going to get lots of attacking chances and that’s Darnell McIntosh doing brilliantly to go 50m upfield but then it’s a wasted opportunity.
There’s a bit of desperation about the way Hull are having to defend with a man down, there is space everywhere.
It looks rather ominous.
Image source, PA MediaHull FC 12-18 St Helens
St Helens pile on the pressure and are camped inside Hull's 10 but the tackles tick down.
A desperate kick on the last is eventually spilled and the hosts win back possession, with Darnell McIntosh racing down the field.
Meanwhile, Adam Swift collects a forward pass and a promising Hull attack comes to an end.
Hull FC 12-18 St Helens
John Kear
Wales coach on BBC One
Hull will have to dig deep now to have any chance whatsoever.
Hull FC 12-18 St Helens
If you're just joining us, this is probably the biggest talking point of the match so far.
Hull's Josh Griffin sees yellow and then red within seconds of the half-time hooter.
The hosts are playing this second half with 12 men and St Helens look comfortable after Curtis Sironen's try.
'Red card a hammer-blow to Hull'
Hull FC 12-18 St Helens
Brian Noble
Ex-Great Britain coach on BBC Radio 5 Live
Saints punch some holes and Curtis Sironen runs a good line and Hull don’t have the numbers in defence.
It was question of Sironen running hard and strong and Saints get the break to increase the pressure on this 12-man Hull side.
Curtis Sironen, goal Joey Lussick
Image source, SWPix.comSt Helens retake the lead!
Curtis Sironen crashes over from Lewis Dodd's offload with some tremendous power while under pressure from the Hull back line.
Joey Lussick adds the two.
Hull FC 12-12 St Helens
John Kear
Wales coach on BBC One
It was just a chaotic end wasn’t it.
He spills the ball and that was a certain four points gone begging.
Hull FC 12-12 St Helens
Joe Batchelor is almost in for his second St Helens try of the afternoon.
Jonny Lomax sends a sensational kick towards goal and Batchelor tries to get on the end of it but it takes a wayward bounce and he spills the ball and knocks on.
A let off for Hull.
Hull FC 12-12 St Helens
Right then.
A frantic first half ended all square and with a red card.
Hull are going to have to dig in deep with 12 men if they are to beat St Helens and reach the Challenge Cup semi-finals.
The hosts get the second half under way.
HT: Hull FC 12-12 St Helens
Mark Chapman has just said on BBC One that supposedly Josh Griffin's inital yellow card was for arguing over being penalised for giving away a penalty - following a coming together with Konrad Hurrell.
That's a pretty minor thing to remonstrate with the referee about in the first place, to me.
And to then get himself sent off is staggering.
'Red card a hammer-blow to Hull'
HT: Hull FC 12-12 St Helens
Brian Noble
Ex-Great Britain coach on BBC Radio 5 Live
Massive blow. It’ll be really interesting to see what happened there because that’s a game-changer.
I would be incandescent if it was Griffin gobbing off at the ref, it’s not necessary, you’re never going to change the ref’s mind on anything let alone after the whistle.
They’re coach killers, that is a sickener.
This game was in the balance but that decision from Griffin, if it’s a poor decision in what he said, it will be the difference between the two teams.
HT: Hull FC 12-12 St Helens
David Beeston: Watching Konrad Hurrell trying to defend. Makes you wonder why Wigan didn’t try and target him more last week. Shocker.
Stevie Essex: Feigning illness to get out of a seven-year-old's birthday party to stay at home to watch the Ashes and the rugby whilst drinking beer has to be up there with one of the best decisions I’ve ever made.
Not sure what to say about that, Stevie...
Hull FC 12-12 St Helens
John Kear
Wales coach on BBC One
That’s worth a shot for me.
A decent decision, just not executed well enough
Hull FC 12-12 St Helens
Image source, PA MediaThe first half comes to an end but there's still drama AFTER the hooter.
Hull's Josh Griffin argues with referee Chris Kendall as the teams head to the tunnel and receives a yellow card.
But he carries on and then is sent straight off!
What a way to end the half. That's a massive blow for the hosts.
Hull FC 12-12 St Helens
Jake Trueman goes for a drop-goal and to be fair to him, he's within a decent kicking range.
Unfortunately for the Hull man, he's not executed it too well and it limps wide.
Hull FC 12-12 St Helens
Tex Hoy offloads to Adam Swift as Hull look to gain a points advantage heading into the break.
But Swift spills the ball and knocks on, thwarting what seemed to be a blossoming attack in the St Helens half of the field.
Hull FC 12-12 St Helens
Brian Noble
Ex-Great Britain coach on BBC Radio 5 Live
Konrad Hurrell hugs the touchline and then the floated pass comes and he scuttles in at the corner to bring Saints level.
Konrad Hurrell
Image source, SWPix.comSt Helens are back in this tie!
The visitors shift the ball from left to right and, you guessed it, Jack Welsby sends through the crucial pass for Konrad Hurrell to race in at the corner.
With Tommy Makinson off, Joey Lussick stands over the tee but he misses the two.
It's all square!
Hull FC 12-8 St Helens
Callum Thompson: Happy for Andre Savelio after a tough few months. He's responded in the best way possible. Some of the collisions in this game. We'll miss the 'Big Bopper' when he leaves.
Southstander: Hull FC look well up for this.