The Portugal captain spoke to Spanish newspaper Mundo Deportivo and said it "hurt" to see Messi take his leave of the international stage following last month's Copa America Centenario final defeat to Chile, per MailOnline's Tom Bassam:
"Messi has taken a tough decision and people should understand. He is not accustomed to defeats and disappointments, not even finish the second. Missing a penalty does not make you a bad player. It hurts to see Messi in tears, and I hope he returns to his country, because he needs it."
Ronaldo can sympathise with his Barca counterpart as one who has never tasted success at a major international tournament, and Messi's latest disappointment was seemingly the final straw.
Messi blazed his spot-kick attempt in the penalty-shootout defeat over the bar in what was a similar blow to their 2015 loss to Chile in the final of the same competition, having been considered Copa favourites.
Portugal's leader is attempting to end his own rut as he prepares for a Euro 2016 semi-final against Wales on Wednesday, hoping to go one better than the final defeat to Greece 12 years ago.
Messi's decision to end his involvement with the national team hasn't been easily accepted by fans, however, as Argentinians descended upon their capital in protest this week:
That public outcry is a gesture of just how adored Messi is among his fans, and Portugal losing the services of Ronaldo would be a similar handicap, if not even more severe given Argentina's depth in quality.
Ronaldo's words of encouragement come as a small surprise given that he's regularly illustrated as a nemesis to the South American, and ESPN FC's Jake Cohen used recent news to compare what it would mean for the two to play together in club football:
Messi, 29, could yet reverse his decision to retire and come back to the national team in time for the 2018 World Cup in Russia, perhaps his chance to have one final international duel against Ronaldo.
They say competition brings the best out of players, and neutrals can only hope both men prolong their international careers for as long as possible.