The two clubs have been in constant dialogue over the past week or so, as billionaire owner Peter Lim is intent on making the Argentine international his first major signing since taking over Valencia last month.
The reported fee agreed is €25 million (£20m) upfront, with further bonuses to be paid to the Portuguese outfit based on of player performances and Champions League qualification over the next couple of years.
The 28-year-old midfielder moved to the Lisbon-based club in 2011, signing a five-year deal for a fee around €5.5m (£4.4m) from Argentine side Godoy Cruz.
Perez's development at Benfica under current boss Jorge Jesus was there for all to see, and he established an excellent understanding with now Chelsea midfielder Nemanja Matic.
His form last season during Benfica’s treble-winning campaign captured interest from Europe’s biggest clubs, with United seeing him as a realistic candidate to solve their midfield crisis.
Described as hard-working, technically brilliant with a wide range of passing, he is ideal for the Red Devils, and new boss Louis van Gaal perhaps should have made more of an effort to bring him in.
United’s loss could certainly be Valencia’s gain. However, despite a fee being agreed, the Spanish paper didn’t hold back in spelling out the situation, as their headline for the report was: ‘For the arrival of Enzo Perez, all that’s missing is his signature’.
While the La Liga outfit will be confident of getting the deal over the line, until the player’s signature is on the contract, there is still time for another club to attempt a last-ditch hijack bid.