Doncaster Knights failed to improve on fourth place as they suffered a 22-5 defeat at home to league leaders London Irish in their final game of the regular Championship season.
They will therefore meet the Exiles over two legs in the play-off semi-finals with second-placed Yorkshire Carnegie tackling Ealing in the other tie.
Having lost just one league game all season, and completed the double over the Castle Park side, Irish will be hot favourites for an immediate return to the Premiership.
But despite being well below their best at windswept Castle Park Knights showed enough to suggest that Irish’s passage into the final will not be a mere formality.
An air of invincibility has surrounded the Exiles for most of the season, but for long periods there was little between the sides.
Irish were tighter in defence and made better use of their chances. But Knights, for whom centre Andy Bulumakua was always a threat, will go into the play-off games convinced that the Exiles are beatable if they bring their A game.
Knights made the better start and had scrum-half Michael Heaney had quicker support after intercepting in his own half they could have scored an early try.
But Irish, who hadn’t breached the Doncaster 22, who took the lead with a penalty by full-back Thomas Bell.
Just when it looked as though Bell’s penalty would separate the sides at the break, a handling error set up the attacking position in the Doncaster half from which Irish wing Alex Lewington cut inside and showed good pace to go over for an unconverted try.
There was still everything for Knights to play for at the start of the second half. But a converted penalty try within minutes of the restart, after hooker Ben Hunter - subsequently sin-binned - had infringed at a driving maul, saw them trail 15-0.
Centres Theo Brophy and Aseli Tikoirotuma combined well to send scrum-half Brendan McKibbin over for another converted try a few minutes later and it was effectively ‘game over’ for 14-man Knights.
To their credit, and they were helped by Irish having two players sin-binned, Knights started to find more fluency in attack and wing Dougie Flockhart went close on several occasions.
Fellow wing Tyson Lewis let Irish off the hook when electing to back himself with a two-man overlap on his right.
Just when it looked as though Irish, 19-0 winners at the Madejski Stadium on the opening day of the season, would deny Knights a score for the second time this season, Lewis touched down in the corner for a last-minute try after latching on to a neat kick by fly-half Simon Humberstone.
Flockhart’s conversion hit the post.
n Knights: Scanlon, Flockhart, Bulumakau, Hayes, Tyson, Cusack, Heaney; List, Hunter,Sprotson, Challinor, Young, Shaw, Hills, Carpenter. Reps: Bergmanas, Nelson, Quigley, Williams,, Makaafi, Edgerley, Humberstone.