Mariano re-signed with Real on Wednesday.
"As far as Mariano is concerned, things have not gone according to plan, as he didn't match the profile of the player that Real Madrid wanted to sign," Aulas told the press conference.
"He wanted to leave and keeping a player against his will is a bad option before a new season.
"We listened to the offers, the one from Seville arrived without being requested and we agreed.
"We didn't know that Real Madrid were going to exercise the clause, but they activated it.
"They will pay 33 million euros plus three in bonuses, minus the 35 percent of the player's rights that they own (ie about 20 million euros)."