Widnes suffered relegation after seven years in Super League as they suffered a 20-12 defeat to Toronto Wolfpack.
Two more Championship sides, Toulouse, who beat Hull KR 34-23, and London Broncos, who beat Salford 11-8, also won against Super League opposition.
It means the make-up of the top tier in 2019 is still to be decided going into the last weekend of the season.
On Sunday, 2017 Super League champions Leeds ensure survival by defeating bottom place Halifax 34-6.
Leeds will take on Toronto Wolfpack next Friday 28 September in Headingley.
Leeds director of rugby Kevin Sinfield said: “At the minute it’s in our hands. Why would we allow it to come down to points difference and everyone getting their calculators out?
“Toronto will be desperate but it’s our last home game of the year. We’ve not been great all year and it’d be really nice to send the fans home on Friday knowing we’re on the right track.”
But there are still a lot of gaps to fill over the course of four days next week – with just two points separating all top six clubs.
Even before the Million Pound Game on Saturday 7 October between the two sides finishing fourth and fifth, none of the eight teams in The Qualifiers have yet ensured a top-three finish to secure a place in Super League for next season.