Doncaster lost their last match 24-10 against Dewsbury, prompting coach Tony Miller to admit his side needs to make major improvements in the final week of the regular season.
Miller said: “Unless we dramatically improve we won’t make an impact on the play-offs.
“We need to hit a bit of form and take confidence into the play-offs.”
Defeat for the Knights would confirm their relegation to Kingstone Press Championship One.
Thornton said: “It’s becoming pretty desperate for us now, there’s no doubting that.
“If we lose, then the trip to Batley (on Sunday) will be totally irrelevant.”