Both the Red Devils and Juve are expected to be in the hunt for a right-back this summer, and Italian website Calciomercato.com (h/t Daily Mirror) reported Cancelo will be a target for the pair. Inter have a £30 million option to sign the player at the end of this season.
Antonio Valencia is United's first choice in that role, but the Ecuadorian will turn 33 in August and has a contract that's due to expire at the end of next season, albeit with the option to add another year.
Cancelo, 23, could therefore face a transition period to become first choice at Old Trafford if he were to arrive, especially after boss Jose Mourinho piled praise on his captain this season, per The Independent:
Juve, on the other hand, are in more desperate need of reinforcements in the position as they prepare to bid farewell to Stephan Lichtsteiner, 34, whose contract will expire in June.
Italy international Mattia De Sciglio has provided another option on the right side of defence but perhaps isn't to the standard the Bianconeri desire, while football writer David Amoyal praised Cancelo's progress at Inter earlier this year:
The Nerazzurri may be priced out of a move for Cancelo, however, and United or Juve would be more financially prepared to pay a sum like the £30 million option in his Inter contract.
Tuttosport (h/t Football Espana) reported Inter want Los Che to trigger their €25 million (£21.9 million) option to sign Geoffrey Kondogbia—on loan at the Mestalla—to help facilitate their purchase of Cancelo in a sort of swap.
Valencia could look to charge even more than that, however, in the event Inter don't take up the option. Football writer Lars Pollmann recently joked that Inter might not handle Cancelo well if they signed him permanently:
The Portuguese has recorded two assists in 10 Serie A starts this season but showed his defensive frailty when he was sent off in Portugal's 3-0 friendly defeat against the Netherlands on Monday.
One tactic United could look to employ would be the promise of cut-price defender Matteo Darmian moving in the opposite direction, with Yahoo's Andrew Gaffney having noted those links during the winter transfer window:
Andrew Gaffney @GaffneyVLC
Valencia are interested in #MUFC's Matteo Darmian after being rejected in their attempts to recall Joao Cancelo from his loan at Inter. No offer has been made to United or the player so far. The deal is complicated due to the probable cost (Valencia have a tight budget). #LaLiga https://t.co/Xgi4S1G8sE
Los Che could land a replacement if that kind of deal was revived in the summer, when negotiations could be affected by whether or not Cancelo makes Fernando Santos' Portugal squad for the 2018 FIFA World Cup.
Serie A titans Juventus will offer capable competition in the hunt for Cancelo, particularly if the player takes a liking to Italian football, but United's need to unearth an heir to Valencia could drive them to move quickly.