Ronaldo spent nine years playing for Real Madrid before joining Juventus for €100 million in 2018. The transfer was viewed as a setback for the Spanish league's international image, with predictions at the time suggesting it could even bring financial consequences, but La Liga president Tebas said the Portugal international's exit had "almost no impact."
In contrast, Tebas said that if Messi were to swap Barca for another club outside of Spain, the league would suffer as a result.
"Cristiano's departure, even though it annoyed Madrid, had almost no impact because La Liga has spent years ensuring that the brand transcends the players," Tebas told RAC1 on Thursday.
"But Messi's case is different. Messi is the best player in the history of the game. We have been lucky to have him in La Liga for his whole career. I think you would notice Messi's departure -- especially if he went to another league.
"It would not be a catastrophe [if he did leave] because we have television deals signed with or without Messi, but the important thing is the value adds. Messi always delights us."
The on-pitch rivalry between Messi and Ronaldo was one of the league's central themes for over a decade, with the two sharing 11 of the last 12 Ballon d'Or trophies between them. Only Luka Modric, in 2018, has managed to break the hegemony in that time.
Messi, who turns 33 next week, is out of contract next summer and, if he does not sign a new deal, would be free to negotiate with potential suitors in January.
"Messi is an icon of Spanish football and I would ask him, please, to finish [his career] in our competition," Tebas added. "We have given him so much affection."
ESPN revealed earlier this month that the clause allowing Messi to walk away from Barca for free this summer has now expired. He signed his terms in 2017 and, at the time, a clause was included that he could leave for nothing in summer 2020 as long as he communicated his decision to Barca before June.
Barca now hope to tie Messi down to another new deal as he moves into the final years of his career. The club's president, Josep Maria Bartomeu, wants to make sure the six-time world player of the year has agreed to new terms before his own mandate expires in 2021.
Bartomeu has previously spoken about offering Messi a lifetime contract, similar to the one signed by Andres Iniesta, and hopes to begin talks with Messi's father, Jorge, who is in Argentina, when some form of normalcy returns following the coronavirus crisis.