I don't think Djokovic has any realistic chance to defeat Nadal in a RG final, just like Nadal has no realistic chance to defeat Djokovic in an AO final. If Nadal reaches the RG final, it will mean he is in good shape. And only Thiem can defeat Nadal there. Thiem is 7 years younger than Nadal, Djokovic is only 11 months younger than Nadal. Djokovic doesn't have Thiem's age advantage. At some point, Nadal will decline enough to allow Thiem start winning RG.Wasn't a choke. Del Potro lost because he's supposed to lose. Can't blame everything to a choke. Djokovic is just the better player.
Also, if they meet in the RG final this year, Novak will need to play in god form because Nadal's B level is good enough to wipe the court with anyone. And nadal always raises his game for the RG finals.