EXCLUSIVE By Alberto Pinero Follow Goal UK on Twitter
Madrid were keen to sign the Argentina international during his time at Atletico between 2006 and 2011, but the Vicente Calderon side refused to sell their star player to their arch-rivals.
He ultimately joined City instead, but a number of reports have now suggested Madrid are back in for Aguero, though Saul wouldn't have any issue with the striker moving to the Bernabeu.
"Aguero to Madrid? I don't mind if he were to join Madrid now," Saul told Goal.
The midfielder, 21, then went on to voice his delight with Atletico's development under Diego Simeone in recent years, having won La Liga in 2013/14 and finished third this time around.
"What Atletico have achieved is simply incredible. Not too long ago, Atletico were still playing in the second tier.
"The club is healthy again now, growing on the pitch and Europe fears us because of our playing style and attitude. We have had a great season and the team deserves a 10 for its performances."
The Spain Under-21 international also briefly discussed his future and says he has no interest in leaving the club after breaking into the first team this season.
"I will stay at Atletico, there is no doubt about that," he said. "I just signed a new deal with Atleti. I have always wanted to be at this club."
Saul signed a long-term five-year deal in May which ties him to the club until the summer of 2020.