The 17-year-old, who has turned out for Cerro Porteno's first team on 17 occasions, is regarded as one of the biggest young talents in South America, with a number of clubs believed to be interested in his signature.
According to transfer expert Fabrizio Romano, Man United are in talks with the left-back's Paraguayan club over a £3.1m transfer, while discussions are also said to have taken place with Leon's agents.
Leon has been with Cerro Porteno since the age of 13, progressing through the various youth teams at the club before making his first-team debut in August 2024, and he has since become an important player for the Blue and Reds.
Arsenal have also previously been credited with an interest in the teenager, but it is believed that Man United are at the head of the queue, with the Red Devils looking to bring another outstanding young talent to Old Trafford.
Man United 'in active talks' over Leon transfer
Paraguayan football expert Roberto Rojas has called Leon "a player with a lot of promise".
"He's a player with a lot of promise, who happened to make this big jump into the first team at Cerro Porteño so quickly," Rojas told transfermarkt. "He's definitely viewed highly because of his talent and recent performances for one of the biggest clubs in the country and occupying that left flank as a full-back has allowed him to be someone who can go onto the attack, start playing from the back and also be versatile.
"Paraguay have recently developed some really good left-backs, so this would be another one to be part of the mix if he were to ever get called up to the national team.
"The links to European football have shown that Leon is a different case, especially at such a young age. It remains to be seen what his ceiling will be, but from the start, it shows he has something that can be very important in the future.
"Like any 17-year-old with little experience playing professionally, Leon is still raw and has a lot he can improve on before making a big jump outside the country."
What is the left-back situation at Man United?
Man United have made signing a new left-back next year a priority, and with Leon viewed as one for the future rather than the present, it is likely that he would arrive alongside an experienced player in that area of the field.
Luke Shaw is injured again, while Tyrell Malacia is only just back from a lengthy absence with a knee problem; Diogo Dalot continues to be used as a left-sided wing-back in Ruben Amorim's 3-4-3 system, but the Portuguese has looked uncomfortable in the role.
As a result, a specialist in that position is set to arrive in 2025, with Red Devils head coach Amorim thought to view that area as one of his main priorities to improve.
Alphonso Davies is said to be 'the dream target', with the Canada international's contract at Bayern Munich due to expire next summer, while Bournemouth's Milos Kerkez is also thought to be a genuine option for the Red Devils, who will return to action against Viktoria Plzen in the Europa League on Thursday night.
Written by
Matt Law