Jackson believes that the Dutch international defender will not be the last big name to leave the Scottish Premier League having been told that his club can no longer afford their substantial salaries.
But he is hopeful that it is a sign that football is "bottoming out" of the worst financial crisis ever to hit the game in Scotland.
Numan had offered to take a pay cut to extend his stay at Ibrox beyond five years.
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I think it is quite good that reality has kicked in
"
Motherwell administrator Bryan Jackson
But it is suggested that he rejected the suggestion of a pay-as-you-play deal offered by SPL leaders suffering from massive debts.
Jackson, also administrator to Clydebank, who last season exited the Scottish Football League due to financial problems, told BBC's Reporting Scotland programme: "If all the clubs start to take that attitude, players will not like to hear it, but wages will come down and the industry will be through its worst.
"I think it is quite good that reality has kicked in, even with the big clubs."
Veteran Argentine World Cup striker Claudio Caniggia is another likely to leave Rangers at the end of the season.
"I think, overall, there will be a lot more players leaving and I think we will see more youngsters given a chance, as is the case at Motherwell, and that can only be good for Scottish football," said Jackson.
Motherwell are still no closer to finding a buyer after more than 10 months in administration and Jackson does not believe that one will be found until overheads in the industry overall come down in line with turnover.
However, he stressed that Motherwell were now operating at break even, were not under pressure to sell players and that he hoped to attract a buyer in time to begin negotiations during the summer break.
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Installing undersoil heating is not in the budget at the moment
"
Motherwell administrator Bryan Jackson
The club's finances were not helped by the loss of nearly £100,000 from Saturday's postponement of their televised home league match against Celtic.
Motherwell launched their own internal inquiry into why their system failed to beat the frost and have written an explanation to the SPL in the hope of avoiding a fine for breaching league rules requiring adequate pitch protection.
"Installing undersoil heating is not in the budget at the moment and we do have pitch protection," said Jackson.
"We had technical problems with it on Saturday, but it has worked well over the years and we are confident it was a one-off situation.
"As far as we are concerned, we are not in breach of any regulations."
Motherwell hope to have the pitch playable for Wednesday's league visit by Dunfermline Athletic.