Former Sinn Fein MLA Daithi McKay believes that Martin McGuinness' time as Deputy First Minister could be coming to an end.
Writing in his Belfast Telegraph column today, Mr McKay has predicted a "changing of the guard" within Sinn Fein and the Stormont Executive in 2017.
Mr McGuinness is currently receiving treatment for an unknown illness, with Sinn Fein declining to give any more information on the nature of the condition.
Party president Gerry Adams recently admitted his colleague's poor health was making efforts to ensure the stability of the political institutions here "even more problematic at this time".
Former Stormont finance committee chairman McKay - who resigned as an MLA earlier this year in the aftermath of the Nama 'coaching' scandal - said: "There have been signs over the past few months that both Gerry Adams and Martin McGuinness would step down in the next couple of years, but that process seems to be gathering speed.
"Over the past two weeks there have been plenty of references to Martin's health, so that may be a signal that changes are coming.
"Gerry Adams has commented on Martin's health in a number of interviews, but at the end of the day it will be down to Martin McGuinness himself and the party leadership."
Mr McKay believes it will be a "hugely significant moment" when Mr McGuinness steps down as Deputy First Minister.
"Martin McGuinness has overseen a decade of stability in the Assembly and Executive.
"He has worked alongside three DUP First Ministers.
"He has kept the partnership ethos together within the Executive, even through the difficulties with Peter Robinson, and also in the past week with Arlene Foster."
Mr McKay has tipped Newry and Armagh MLA Conor Murphy to succeed Mr McGuinness when he decides to step down.
And he believes the "changing of the guard" could lead to a more fractious relationship between Sinn Fein and the DUP.
In his column, Mr McKay writes: "McGuinness has been in post for almost 10 years, served alongside three different DUP First Ministers and demonstrated rationality and patience throughout. A patience and resolve that was required to bed the institutions down.
"His successor may not show the same forbearance. The Renewable Heating Incentive debacle is the latest in a long string of DUP scandals including Nama, Red Sky and the Giant's Causeway Visitors' Centre.
"Sinn Fein's desire to make this Executive work requires a careful balancing act. Republican strategy requires stable government in the north. That political strategy may now have to take a hit for the party's own credibility."
Mr McKay added: "I think the partnership between the First Minister and Deputy First Minister reverberates throughout the rest of the Executive in terms of party relations.
"Martin has shown great patience in recent weeks with regards the RHI and Arlene Foster's response to the scandal.
"If she continues in the same vein, I am not sure whether other republicans will show the same patience."