The champions never recovered from the shock of conceding three tries inside the first 14 minutes to trail 18-0 and finished a well-beaten side, although Cunningham said he had seen advance signs of the “debacle”.
“This has been on the horizon,” Cunningham said. “We weren’t great against (Castleford), we weren’t great for 50-plus minutes against Widnes and tonight we started the game horribly.
“As coach I’ve got to take the brunt of this and, as a local boy who’s a spectator and an ex-player, I want to apologise to all the Saints fans who made the journey on a Friday evening to come across and watch that debacle.
“It was probably the worst start in St Helens’ history, I don’t think I’ve seen a poorer start.”
Those early tries from Kallum Watkins, Kylie Leuluai and Ryan Hall put Leeds firmly in the driving seat and 19-year-old winger Ash Handley added a fourth just before half-time on his way to completing a second hat-trick of the season against St Helens, having also made his mark in the Rhinos’ 41-16 victory at Langtree Park in April.
Cunningham added: “You’d learn lessons from the last time we played Leeds. If you give them chances, they will score tries.
“By the time we maintained some form of composure, we were chasing 22 points, and that’s just not good enough. Expectations are high at this club. We like to think we’re a world-class club and that’s not good enough.
“A lot of senior players let their team-mates down today. Amongst it all there was actually some good defensive stuff but it was too little, too late.
“Jon Wilkin was tireless in leading from the front and it’s a pity 16 blokes didn’t go with him.”
Cunningham knows he has plenty of work to do before his side takes on Leeds for a place at Wembley but the July 30 Challenge Cup semi-final was not at the forefront of his thoughts.
“There’s plenty of time before we roll into a semi-final,” he said. “We’ve got Huddersfield to worry about next week.”
The Rhinos’ eight-try triumph enabled them to go three points clear of St Helens with just three games left of the regular season before the split for the new Super 8s.
“We nailed our chances early,” said Leeds coach Brian McDermott. “I don’t think we were actually that dominant. We were not brilliant but we did score 22 points in that first half.
“We were really clinical when we got the chance to score.”
McDermott was encouraged by the debut of Australian prop Mitch Garbutt and delighted with the contribution of back-rowers Brett Delaney, Carl Ablett and Jimmy Keinhorst as well as the try-scoring exploits of Handley.
“He must be very pleased,” McDermott said. “Because he’s young, people continue to have a crack at him and he keeps coming up with the answers.
“He’s got a fair amount of work rate in him as well as some of the nice finishes.”