Herrera, who made the Premier League pilgrimage from hometown Athletic Bilbao in 2014, has made 187 United appearances and earned the Sir Matt Busby Player of the Year award for the 2016-17 campaign.
However, he's been a frequent topic of transfer reports this season as one of several United first-team players with contracts set to expire. Antonio Valencia, Matteo Darmian, Juan Mata and Andreas Pereira could all be joining Herrera as part of a substantial summer exodus while United look to refresh their squad ahead of Ole Gunnar Solskjaer's first full season in charge.
"As it is right now, Manchester and I are not thinking alike," Herrera recently told Diario ABC, as translated by BBC Sport.
For PSG, the 29-year-old Herrera's arrival would bolster a sturdy midfield that already features Marco Verratti, Leandro Paredes, and center-back-cum-defensive midfielder Marquinhos.