Links between arguably the Premier League's best custodian - formerly of Real's cross-city rivals Atletico - and the reigning La Liga and European champions are typically revived during every transfer window and in September 2015 a proposed £29m ($39.1m) switch collapsed after the necessary paperwork was not submitted in time.
De Gea, who signed a lucrative new four-year contract with United on wages of around £200,000-a-week soon after that failure, has gone from strength to strength since then and in 2016 became the first man ever to win the Sir Matt Busby Player of the Year award in three consecutive seasons.
The 26-year-old has attracted yet more praise of late thanks to stunning saves to deny Stoke City forward Jese Rodriguez and former teammate Wayne Rooney and Herrera believes his compatriot - whom he describes as having a "a gift that comes from God" - will remain at Old Trafford for the foreseeable future provided the in-form Red Devils can quickly add to the three trophies they collected during Jose Mourinho's first campaign at the helm.
"We are going to enjoy having him here and try to keep him at the club for as long as possible," he was quoted as saying by The Telegraph. "I think he wants to be a legend in the club, which is important for us. Of course I can see him staying here for more years. How good is David now? We need to win titles to keep him with us. That is what we did last season."
Herrera believes that Real will continue to discuss a potential move for De Gea, although remains confident that United, who have opened the 2017-18 campaign by winning six of their first eight matches across all competitions while scoring 20 goals and conceding just three, are not currently too far behind Los Blancos in terms of their development.
"David is really happy at the moment because we are fighting for everything," he added. "We won three titles last season [the Europa League, EFL Cup and Community Shield], and the FA Cup the year before, and that is what he wants. Real Madrid are going to talk about it every summer because he is the best keeper in the world. But we don't think we are far from Real Madrid, we won three titles last season, the only English team to do it."
Reports in July stated that Real were once again set to revisit their interest in De Gea, although Mourinho quickly offered a "100%" guarantee that he would not be sold amid conflicting speculation over a £60m bid. Marca claim that manager Zinedine Zidane actually blocked any possible move for the Spaniard, Chelsea's Thibaut Courtois or AC Milan teenager Gianluigi Donnarumma due to his unwavering faith in current number one Keylor Navas.
The saga will likely be revived next year, with suggestions that Real president Florentino Perez wants De Gea to replace Navas and will swoop after the 2018 World Cup in Russia.