The 31-year-old Ecuadorian international, converted from a winger to a wing-back at Old Trafford, has enjoyed regular starts under Mourinho with the new United boss impressed by his pace and power.
Valencia, who has played in ten of United’s twelve League games this season, has won two League titles, an FA Cup and League Cup in his seven years at Old Trafford since joining from Wigan in a £16 million deal.
And Mourinho believes the South American star still has plenty more to offer with the player also happy to stay at Old Trafford.
Mourinho said: “Big clubs like Manchester United want to keep their best player and the best players at the biggest clubs want to stay for the rest of their career.”
Valencia has fully transformed into a dependable right-back and has featured 13 times already this term to become one of Mourinho’s most trusted players.
Once Valencia finishes the final-year option on his deal, he will have played for United for nine years.