Gareth O’Brien’s crucial one pointer was Castleford’s NINTH attempted drop-goal in the fourth period of Golden Point extra-time and came as late as the 99th minute in a remarkable third round tie.
The outcome was brutal on winless Hull KR who lost in Golden Point for the second time in three games this term.
They had led 22-6 at half-time and then 32-18 with only nine minutes remaining, only to see brilliant Man of Steel Paul McShane inspire Castleford’s surreal fightback.
Derrell Olpherts dashed in for his second try and, with just four minutes remaining, hooker McShane dummied over for his double for Danny Richardson to make it 32-28.
Then, with the final play of normal time and the hooter having already sounded, Castleford kept the ball alive wonderfully before McShane produced yet more wizardry to put Jordan Turner in to level.
Richardson could not convert meaning the game went into extra-time where Tigers had countless chances to win only to see Richardason, Jake Trueman and O’Brien all miss with drop goal efforts.
Rovers were restricted to just two such attempts but O’Brien - who famously relegated Rovers with a Golden Point drop-goal for Salford Red Devils in the 2016 Million Pound Games - eventually held his nerve.
Trueman scored Castleford's other try and Powell said: “It was absolute madness.
“I've never seen anything like it in my life.
"It was a crazy game and we were fortunate to win it, to be honest.
"In the first half in particular we were really poor and Hull KR were superb; from that perspective, they probably deserved to win.
"But in the second half, I was pleased with our character. We had to find a way back into the game and we dominated the start of the second half.
“Yet in (almost) 20 minutes of Golden Point, we can't drop a goal....
“I've been in to the halves for a fair while about that so I think they believe me now that it’s actually going to win you a game here and there.”
After Turner levelled the game, with his fourth try in three outings since joining from Huddersfield Giants, Powell hoped his side would have secured their place in Saturday’s quarter-final draw more swiftly.
“We’ve got a goal kick to win it then so we’re thinking just get this and we can get ourselves off feeling pretty happy with ourselves and a bit fortunate to get into the next round,” he said.
“But what happened after that was just crazy really.
“I don’t think either team had a great strategy to win a Golden Point game but fortunately we were the team to come out on the other side of it.”
Both sides showed tremendous endurance in extra-time when there was hardly any handling mistakes and defences continually battled to shut down drop goal opportunities, Castleford twice being charged down despite some Rovers players looking like they were out on their feet.
On his side, whose pack continually got them in good positions, Powell admitted: “It’s certainly going to test your fitness.
“The boys in the middle were running on fumes. They’ve never played that long before. I don’t think anyone in the team has.
“It was tough on both teams. It was a real energy zapper. There’s no replays now so you have to deal with it tonight. It was just a slog. And a battle.”
Ironically, O’Brien - who struck that monster drop goal effort on the same ground to break Rovers hearts five years ago - was only playing because regular No1 Niall Evalds was sidelined.
Powell explained: “His partner’s having a baby and he’s been in hospital with her.
“It started the other day and just extended so I just said to look after his family and we’d see him next week.”
Hull KR chief Tony Smith struggled to put his thoughts into words.
They had been brilliant in spells, not least in the first period when they took such a hold with tries from Adam Quinlan, Matt Parcell and Albert Vete following Ethan Ryan's opener.
After Castleford rallied at the start of the second period, the hosts hit back once more with excellent Shaun Kenny-Dowall and Jordan Abdull tries only for their opponents to somehow surge back again.
"People were out on their feet; I can't criticise them for their efforts," said Smith.
"The effort from both teams was enormous.
"We made progress in a lot of areas. There was enormous improvement in our defence; we dominated the defence for big periods of the game, which was outstanding and there were times in that match when we were in control.
"They are one of the teams people are tipping for all sorts this year so to go toe to toe with them was outstanding.
"I am pleased we were able to show what we can do but at the same time disappointed we didn't go on with it."