Casillas, who is on a considerable wage at the Portuguese club despite only being the second-choice stopper, wants to challenge himself with a move to England, according to The Mirror.
The move could also be beneficial to Porto, who are looking to avoid a Financial Fair Play charge by cutting their wage bill.
Spain legend Casillas has not played for Porto since October and is believed to have instructed his agent to negotiate a move away from the side.
Casillas's agent has reportedly been in contact with West Bromwich Albion, who could be considered as a suitable next destination.
The 2010 World Cup winner is expected to hold a meeting with his current employers about his future in Portugal.