The NRL season got underway last week and is scheduled to continue behind closed doors from round two.
But there are concerns over the financial impact of playing without fans or the season possibly being suspended due to the coronavirus.
Greenberg said there was a possibility star players may be asked to take pay cuts if the season was hugely impacted.
— NRL (@NRL) March 15, 2020
"We haven't done that yet and again that would be an extraordinary measure," he told the ABC on Monday.
"But we have got within our collective bargaining agreements with our players provisions around what we would call material adverse change which is, the simplest way I can describe it is when revenues fall, costs fall and that would be an industry-wide problem for both our clubs and our players.
"That's something that's available to us, but again that would be an extreme measure."
Rugby league has already asked to be included as part of the Australian government's economic stimulus package.
Greenberg said the NRL had a fund to use while it is impacted, but feels it may not last long enough.
"We do have money put aside and we do have assets on our side," he said.
"But what we're suggesting is that will only last a very short amount of time in an issue like this. It's a much more significant issue."
Photo Getty Images Caption: NRL chief executive Todd Greenberg