|Leeds (16) 22|
|Tries: Watkins, Hall, Moon, Garbutt Goals: Sutcliffe 3|
|Widnes (10) 23|
|Tries: Thompson, Mellor, Ah Van, Hanbury Goals: Hanbury 3 Drop-goal: Mellor|
Joe Mellor struck a dramatic late drop-goal as Widnes Vikings won at Super League champions Leeds to officially end the defence of their title.
Bottom club Leeds, who won the treble last year, must now play in the Qualifiers of the Super 8s.
Kallum Watkins, Ryan Hall and Joel Moon crossed for the hosts at Headingley to open up a 16-10 lead at the break.
But, after Mitch Garbutt's try, Patrick Ah Van and Rhys Hanbury levelled it at 22-22, before Mellor won the game.
In a thrilling contest, the Rhinos knew they had to win their last four games to give them a chance of finishing in the top eight before the Super 8s split.
But, despite Leeds' first-half dominance, Corey Thompson and Joe Mellor crossed in the first 40 minutes to keep Denis Betts' Widnes side in touch.
The Vikings had lost 10 of their past 12 league games coming into the match but victory all but secures them a top-eight finish, as they sit six points ahead of ninth-placed Salford with three games left.
After a torrid season in defence of their title, Brian McDermott's men must now switch to focusing that they stay in the top flight next year.
Leeds head coach Brian McDermott: "It's a dent to the pride, absolutely. That's not what we're about and it's not where we want to be.
"It's where we're at because of certain things that have happened this year that have been out of our control, but at the same time there are things we need to learn. The Kirkstall issue and the injuries have had a huge part to play but we should have learned along the way.
"If you take the context out of the game, that was a good performance.
"The danger is the overreaction to this for everybody involved. We're going to get to a stage where we're playing in the Qualifiers and we need to be as good as we can be."
Widnes head coach Denis Betts: "It's an understatement to say I'm proud of this team.
"There's a resilience building in this team, we could so easily have folded on the back of the massive disappointment in the Challenge Cup.
"Moving on to this week knowing that Leeds are very desperate. They had to win every single game, are at home and have some players back. For us to win this game is very impressive.
"It's a fantastic achievement to all but secure our place in the top eight."
Leeds: Sutcliffe; Briscoe, Watkins, Moon, Hall; McGuire, Burrow; Galloway, Jones-Buchanan, Garbutt, Achurch, Ferres, Singleton.
Replacements: Ablett, Cuthbertson, Keinhorst, Golding.
Widnes: Hanbury; Thompson, Runciman, Marsh, Ah Van; Mellor, Brown; Cahill, White, Buchanan, Houston, Dean, Leuluai.
Replacements: Whitley, Manuokafoa, Dudson, Heremaia.
Referee: Ben Thaler.