Herrington, 18, left Australian side Brisbane Roar for Colorado in January and has made 17 league appearances for the MLS club, scoring once and adding an assist.
He then started for Australia at this summer's World Cup, playing two matches as the Socceroos made an impression despite their limited experience at the highest level, taking his senior international caps to six in total.
That form has attracted some of the biggest names in world football, with Barcelona and Liverpool both credited with interest, alongside Manchester United, Chelsea and Manchester City.
Now, according to journalist Ben Jacobs, it is Premier League newcomers Hull City who are in advanced talks over a deal, with the player himself said to view a move to England positively.
Herrington remains under contract with Colorado until the end of the 2029 season, with an option for a further year, but Jacobs reports the fee is likely to land above £20m — enough to make Herrington the most expensive Australian export in the sport's history, surpassing Harry Souttar's £14.5m move to Leicester City from Stoke in 2023.
Hull have already been active in the transfer market this summer, bringing in goalkeeper Jack Butland, defender Matt Targett and midfielders Oscar Zambrano and Hidemasa Morita as they prepare for a return to the Premier League. Landing Herrington would represent a significant statement of ambition from Sergej Jakirovic's side, who face Manchester United in a high-profile fixture to mark their top-flight return on August 22.
Herrington only turned 18 in July and has played fewer than 40 senior matches in total, having made his first-team breakthrough at Brisbane Roar before an initial €450,000 move to Colorado brought him to MLS.
Despite that lack of experience, he impressed for Colorado alongside more seasoned defenders and was trusted by the Socceroos in high-pressure, must-win fixtures during the World Cup group stage, a level of composure that has done much to fuel the growing interest from Europe's leading clubs.