Stoke could complete the signing of Bruno Martins Indi on Friday but it will not be done in time for him to play in the opening game of the season at Everton.
Potters boss Mark Hughes has been trying to get the 25-year-old centre-half back to the bet365 Stadium on a permanent basis following his successful loan spell last season.
Negotiations with Porto have proved frustrating but it is understood a deal just in excess of £7million has now been agreed and the player has settled his own outstanding contractual issues with the Portuguese club, which had been a contributory factor in delaying the deal.