The teenager made just three starts and 11 substitute appearances at the Buenos Aires club, totalling fewer than 500 minutes on the pitch.
Reports from Ben Jacobs suggest Chelsea's hierarchy have also grown uneasy about the youngster's discipline and conduct away from the pitch during his time in South America. It was decided at the end of the Premier League season that the two clubs would discuss cancelling the loan, and they are understood to be "discussing next steps" two months on.
Paez's path to Chelsea has been a long one: the £17.2m deal for his signature was struck back in 2023, but he stayed in Ecuador to keep developing for another two years before officially arriving in England. Since then he has been shuttled between loan clubs, first to sister side Strasbourg, then, after that spell ended early, to River Plate in search of regular football ahead of the World Cup.
The 19-year-old, who plays in attacking midfield or out wide, had a similarly frustrating time on the international stage, named in Ecuador's World Cup squad but seeing only fleeting involvement. Integrating him into the first team after his struggles in Europe looks unlikely, meaning a third loan could be next, ideally somewhere he can show what he can do.
Miguel Angel Ramirez, academy director at Paez's boyhood club Independiente del Valle when he first caught the eye of European scouts, believes the issue is not about ability.
"Whether he becomes a top player is up to him and his response to this situation - above all, off the pitch," Ramirez told The Sun. "Maybe his development was too fast and the expectations too high, too early. It is not easy to deal with that. Now all the pressure and expectations are on him, and I don't know if he has the tools to respond to those expectations already.
"It is completely up to him if he is able to respond because he has the talent. He is so good. But I don't know if he is able to pay the price as others are doing off the pitch."