The 28-year-old, who was in action for Mexico at the 2018 World Cup, has made almost 200 appearances for Porto since a move from Pachuca in 2013.
The midfielder's current deal will expire at the end of the season, however, and it is understood that he will move on a free transfer next summer.
Tottenham Hotspur and Arsenal have both been credited with an interest, while reports in Spain had claimed that Madrid wanted to sign the Mexican ahead of the 2019-2020 campaign.
Lopetegui, however, has branded the rumours "an invention", with Los Blancos not in the hunt for the midfielder.
"The Hector Herrera rumours are just an invention. I wasn't in Porto, I did go with my family on holidays, but I didn't meet Hector," Lopetegui told reporters.