Fields has tendered her resignation from the ACA in order to pursue career interests away from cricket.
Nicholson was nothing but complimentary for Fields, a former Australian Captain, and her commitment to her role at a particularly challenging time for Australian cricket.
"In 2015 Jodie was a well credentialed candidate for this new role and did an outstanding job throughout her time with the ACA," Nicholson said.
"With womens cricket heading further towards professionalism it was critical that the ACA resourced appropriately to fulfil the many needs of our female members, and Jodie's commitment was exemplary."
The recently completed MOU achieved historic improvements for female players, with Fields playing a vital role in representing the views of the ACA members.
"The MOU ultimately achieved an outcome for female cricket and womens sport that we are all very proud, and something that I hope Jodie takes a lot of personal satisfaction in," Nicholson said.
Fellow former Australian Captain Lisa Sthalekar echoed Nicholson's sentiments.
"Jodie really was an unsung hero throughout the MOU dispute," Sthalekar said.
"She fought at every turn for womens cricket and she deserves a lot of credit for the outstanding MOU outcome.
"Given Jodie's level of professionalism I know she'll be a success wherever she wants to take her career."
Nicholson said that Fields leaves the ACA with his blessing.
"Jodie always gave 110% to her cricket and to the ACA, so we wish her all the very best in the next stage of her professional life."