The 26 year-old has left Atletico's pre-season preparations in order to undertake a medical for Porto with a move to be set for completion in the days coming after the medical.
It is believed that the fee for the former Deportivo La Coruna player would be in the range of 15 million euros which would leave Atletico with a neat sum of money in their pockets but leaves them with just Mario Mandzukic who joined the club very recently and Leo Baptistao in their striking stocks.
Porto have also completed the loan capture of promising young Atletico talent Oliver Torres who spent the back-end of last season on loan at Villarreal.
Adrian was subject to limited game time with David Villa and Diego Costa both regular starters ahead of the two-time Spanish international and because of this was able to scored just 3 goals last season with a further 5 assists being provided.