Michael Regan/Getty Images
Herrera with the Mexican U-23 side
Movement: Up Two
Transfers In: Hector Herrera (Pachuca, £7.5 million), Diego Reyes (Club America, £6 million), Lica (Estoril, Undisclosed), Carlos Eduardo (Estoril, £750,000), Josue (Pacos de Ferreira, Undsiclosed), Tiago Rodrigues (Vitoria de Guimaraes, Undiclosed), Ricardo Pereira (Vitoria de Guimaraes, Undiclosed)
Transfers Out: Joao Moutinho (AS Monaco, £21.5 million), James Rodriguez (AS Monaco, £38.5 million)
While it may be confusing that Porto are ranked so highly given the departure of some of their biggest assets this summer, these rankings are based on business and not just who can bring in the most.
This year, it's Joao Moutinho and James Rodriguez (pictured) that have completed a £60 million double move to AS Monaco, according to BBC Sport.
In the past, Porto have shown the ability to survive the fallout of the sales of some of their best players while maintaining a strong international presence, as well as benefitting financially from such deals.
As such, the club have already begun to rebuff their side after selling the latest batch of stars.
Speaking to Portuguese publication O Jogo (h/t Goal.com), Herrera said that he has "Given his word to Porto" and the 23-year-old will be expected to play in a similar role to the departed Joao Moutinho.
Herrera will accompany fellow Mexican, Diego Reyes, to the Estadio Dragao after Goal.com reported that the former Club America defender would link up with the Portuguese giants for a fee of £6 million.
The official UEFA website recently reported that the Dragons had signed Lica and Carlos Eduardo from Estoril, as well as wrapping up a deal for Pacos de Ferreira's Josue.
It's also been reported on Demotix.com that Porto completed a double swoop for Vitoria de Guimaraes pair, Tiago Rodrigues and Eduardo.