KNIGHTS’ hopes of reaching the play-off semi-finals suffered a devastating blow as Bedford snatched victory from the jaws of defeat.
Tries from Steve Boden and Steve McColl saw a determined Doncaster side come from 10-6 behind to lead 16-10 with ten minutes remaining.
But scrum half Tristan Roberts failed to add to his penalty, and first half drop goal, as he crucially sent both conversion attempts wide.
Doncaster were made to pay when Mike Howard went over for his second try with two minutes remaining, and Myles Dorrian’s successful kick gave Bedford a crucial win at Castle Park.
Roberts’ drop goal, in reply to a Dorrian penalty, were the only scores during an uninspiring first half.
But things opened up after the interval and moments after Roberts’ penalty put Doncaster in front for the first time, Howard’s first try on 57 minutes - converted by Dorrian - saw the visitors take a 10-6 lead.
That scoreline was harsh on a Knights team playing the more fluent rugby and the hosts came storming back when the Doncaster pack drove over the line and Boden touched down.
Roberts missed a relatively straightforward conversion but was presented with another opportunity after Dougie Flockhart set up McColl for a superb turnover try with the clock ticking down.
Sadly Roberts again missed the target - and Doncaster were punished in cruel fashion when Howard powered over the line in the dying moments, and Dorrian made no mistake with the conversion.
The defeat means Knights must win the return Pool B fixture at Bedford on Saturday to stand any realistic chance of reaching the knockout stage.