In the build-up to the match at the Mend-A-Hose Jungle Radford had said he was terrified having seen the Saints squad, which had seen them rest almost all of their senior players.
But although the youthful visitors gave a good account of themselves, particularly in a spirited effort in defence it was a comfortable enough 30-10 victory for the Tigers to add to their Easter wins over Wakefield and Leeds.
“I think we did just enough fortunately,” said Radford.
“I’ve got to give credit to their boys, the enthusiasm they came with.
"Their last score made me a little bit twitchy. Every player of ours was holding a limb in the last 20 minutes and to play three games in eight days is a task and hopefully we’ve come through it okay.
“I thought defensively we were really good, what was really evident was some of the fatigue errors like at the play the ball and dropped balls but I’m pleased we got through it.
“We need some improvement in there obviously, but mentally we attacked it with the right attitude.”
Radford reflected on the difficulties of the game for his team: "If we put 50 points on them it was expected but if it was a close game or we got beat, it's disgusting.
"I was petrified when they scored their last try because they looked fresh-legged and fresh-faced and were playing with energy.
"To respond like we did was pleasing. At that point it was all about territory. Dad's Army' did a good job of killing the game off at the end."
Radford was pleased with his own teenager in Jason Qareqare, who was a late call-up to play n the wing and took his chance with a spectacular try after only 34 seconds.
He added: "Qareqare's try was an unbelievable effort. As a winger you are judged on your try-scoring ratio but he was also fantastic out of back field.
"He has just signed a new deal and I want to see him be the best he can be over the next couple of seasons."
St Helens fielded seven debutants in effectively a second-string team that sent a clear message to the RFL about scheduling three matches in a week while Cas had their share of players missing with Greg Eden, Niall Evalds, Jordan Turner, Danny Richardson, Bureta Faraimo, Suaia Mategi and Cheyse Blair among their absentees.
Despite this it was a decent match, much better in quality than the Easter Monday clash with the Rhinos, and the Tigers had the benefit of their whirlwind start that helped them to their fourth straight Super League win and a record victory over Saints in the summer era.
Moving the ball wide in their first set, Cas gave speedy 18-year-old Qareqare the ball inside his own 20 and he did the rest with a scintillating run down the left wing, beating several defenders to celebrate signing his new deal in spectacular style.
Of course, this was not the first time he has made a quick impact after he also scored a brilliant try in the first minute of his debut against Hull FC last year.
The Tigers dominated the early play, but they missed out on a second try when Derrell Olpherts was unable to finish in the right corner.
Some sloppy play then crept into the Tigers' game and it took them until the 27th minute to add to their lead as Olpherts this time finished well in the corner after s smart move.
Jake Trueman's try five minutes before the break following Jake Mamo's great run had Cas looking comfortable with Paul McShane landed the first goal of the night to make it 14-0.
That was how it stayed to half-time, although Qareqare came close to scoring again when only denied by a superb tackle as he dived for the line.
Qareqare was denied another try early in the second half when he put a foot in touch, but on the other wing Olpherts did score his second after being given the ball in space by Mamo.
Saints then had their best spell of the game as Kyle Amor was held up over the line and Jumah Sambou squeezed over for a try in the corner following an excellent offload by Josh Simm.
The visitors scored again soon after to make it 18-10 as James Bell went over from close range and Shay Martyn goaled.
But their good work was then undone as they lost possession in their own half following the restart and Cas took full advantage with Joe Westerman powering over after backing up McShane's break. McShane added the conversion..
It was all over when Mahe Fonua brushed off several defenders to score Castleford's sixth try and McShane kicked his third goal.
Castleford: Clare; Olpherts, Mamo, Fonua, Qareqare; Trueman, O'Brien; Watts, McShane, Griffin, Edwards, Lawler, Westerman. Subs: Milner, Massey, Smith, Martin.
St Helens: Bennison; Sambou, Simm, Hill, Martyn; Davies, Moss; Amor, Lussick, Norman, Royle, Bell, Wingfield. Subs: Baxter, Pemberton, Delaney, Buckley.
Referee: Jack Smith