Flannery (l) and his team-mates were too good for Senior and co
Leeds coach Brian McClennan admitted he had not expected a 38-10 drubbing by St Helens in the Super League play-offs.
Saints booked their third successive Grand Final appearance with a seven-try home display against the 2007 winners.
"There is a fair degree of shock, we trained well in the week and felt confident going into the match," said New Zealander McClennan.
"I don't think we ever really threatened. We didn't run on to the ball with enough intent."
Leeds must now face the winners of the Catalans Dragons and Wigan game in the final play-off eliminator next Friday at Headingley to maintain any hope of defending their Super League crown.
"We'll take it on the chin. We've a chance to redeem ourselves but we've got a fair bit of work to do," he said.
I was in awe of the quality of performance in the second half
Saints coach Daniel Anderson
Leeds have injury concerns over full-back Brent Webb, who was withdrawn on the hour with a knee injury, although McClennan remains upbeat the New Zealand international will be available next week.
"He suffered a recurrence of the injury he did in training a couple of weeks ago but he's not twisted or torn anything," said McClennan.
"It was just a bang on the knee and we're confident he'll be OK."
Saints coach Daniel Anderson bid farewell to Knowsley Road with yet another commanding performance from his players.
The Australian - who will leave the club at the end of the season to return to his native country - was effusive with his praise.
"I was in awe of the quality of performance in the second half," he said.
"I thought the way we played was brave tonight. You can go into your shell but we played with the style that has exemplified our season.
"It was very satisfying. I thought our unheralded players were very strong."