The sanction affects Batley, in particular, given last season’s beaten Grand Finalists now drop into 10th - crucially, the fifth and final relegation place - three points adrift with just three games remaining.
With the new competition re-structure in place for 2015, when Championship sides have the chance to face Super League teams and earn promotion, demotion into Championship One for John Kear’s men would prove disastrous.
Whitehaven have benefitted from the decision, lifting up to ninth, and, so, Batley’s Heavy Woollen derby with Dewsbury Rams at Mount Pleasant now takes on huge significance.
Doncaster, meanwhile, stay in fourth but are just three points in front of Dewsbury who will hope to chase down Paul Cooke’s side.
Batley and Doncaster were found guilty of breaching Operational Rule B3.17.
That states dual-registration players who have a salary cap value of £20,000 or more must have played in at least three league fixtures for the Championship club that campaign before the end-of-season registration deadline in order to play in games which fall after the deadline, whether they be regular season or play-off games.
The charges were heard by an RFL Operational Tribunal following complaints that Jacob Fairbank, a dual-registered player from Huddersfield Giants, played for Batley in their win against Sheffield Eagles, and that Ben Crooks, a dual-registered player from Hull FC, played for Doncaster as they lost to Keighley Cougars.
Both matches were played on Sunday July 27, two days after the registration deadline for the Championship closed.
Doncaster say they will appeal the ruling.
Chief Executive Carl Hall said: “Whilst we do not dispute Ben played in the game, based on communications and dialogue we have had with the RFL prior to the player participating in the game, we are disappointed with the outcome of the hearing and the punishment that has been provided.
“We can confirm we will be appealing the decision.”
Batley chairman Kevin Nicholas said: “We’re disappointed but we’ll consider an appeal once we’ve got the written reasons.
“We’ve been told that will be in the next seven days and we’re just going to concentrate on winning this Sunday and trying to win the last three games to give ourselves a shot at avoiding relegation.”