Clive Griffiths’s side had to work hard to see off Hartpury 20-8 away in a scrappy first fixture of the league campaign.
The visitors did not make sure of victory until Pete Lucock, the impressive centre signed from Yorkshire Carnegie in the off-season, crossed for a 79th-minute try.
Doncaster will know they must improve in some areas ready for Saturday’s visit from Cornish Pirates who started their season yesterday with an excellent 30-10 win over promotion-chasing Ealing Trailfinders.
Knights saw veteran lock Matt Challinor receive a yellow card for an illegal tackle early on Saturday and it was no surprise, then, that Hartpury opened the scoring via on-loan London Irish lock Chunya Munga.
Doncaster responded when hooker Ben Hunter scored against his former side following a driving maul in the 33rd minute but the hosts opened the scoring in the second period with Joshua Bragman’s penalty.
However, Doncaster’s Sam Olver added two penalties and then helped his side defend hard to repel their opponents before Lucock eased all the tension.
He has been in good form in pre-season and added to his earlier try in Championship Cup action. Olver, who kicked well out of hand, converted to make sure the South Yorkshire club start off on a positive note.
But Cornish, led by former Carnegie director of rugby Chris Stirling, showed what they are capable of with a ruthless destruction of big-spending Ealing.
They raced into a 22-3 interval lead and Ealing, who have ex-Bradford Bulls coach James Lowes on their staff, had no answer.