Impressive as big-spending Ealing were at times in their bonus point 38-22 win at Castle Park, Knights contributed to their downfall with individual errors in both attack and defence.
Even so, Knights will have been disappointed to finish empty-handed for the first time this season after showing great character to get themselves in a position to at least pick up a losing bonus point after trailing 28-8 at one stage in the second half.
Aiming for a third successive win, Knights took an early 3-0 lead courtesy of returning fly-half Kurt Morath.
Ealing took a lead they never lost on 12 minutes when winger James Cordy-Redden got on the end of a cross-field kick to the corner by fly-half Craig Willis. Full-back Peter Lydon added the extras.
Centre Lewis Jones then touchedÂ down near enough for Lydon to again add the extras.
Charles Carter usedÂ his strength and quick feet toÂ set up the chance for Lydon to touch down for a try he also converted to make it 21-3.
Doncaster hooker James Malcolm celebrated his first start for the club when touching down from a catch-and-drive to throw his side a badly-needed lifeline.
Knights knew that they couldn't realistically allow Ealing to score next after the break and made a spirited start to the second half.
But it was the visitors who drew first blood on 46 minutes - Willis picking out Cordy-Redden with a long pass inside the Doncaster 22. Lydon again added the extras.
Traiiing 29-8, it looked like being a damage-limitation exercise for Knights at that stage.
But a tremendous run by replacement prop Joe Sproston with his first touch of the ball set up the position from which wing Curtis Wilson won the race to an astute kick by scrum-half Tom James who later came close to a try following a fine individual effort.
Knights generally competed well in the set-piece and when Ryan scored a third try from a driving maul - superbly converted from touch by Morath - it was game on.
However, Knights' hopes suffered a double blow on 71 minutes when prop Toby Williams was sin-binned and Lydon kicked the resulting penalty to make it 31-22.
Centre Patrick Howard put the result beyond doubt with a late converted try.
Knights: Jarvis, McColl, Hayes, Creed, Wilson, Morath, James; Hislop, Malcolm, Quigley, Challinor, Civetta, Ryan, Calladine, Tyrell. Rep: Nelson, Wiliams, Sproston, Eames, Hicks, Seniloli, Cowell.