Having spent a decade with the Black and Yellows, Subotic insists Dortmund will finish first if Bayern fail to strengthen further this summer having pushed them all the way last season.
Despite the Bavarians bringing in big-money defensive reinforcements in Benjamin Pavard and Lucas Hernandez, Subotic refused to sit on the fence and was clear in who he was backing.
"If the Bayern squad stays the same it is Dortmund. Very clearly," he told Bild .
"I say that as a former BVB player and fan."
While he himself has returned to the Bundesliga, Subotic's former team-mate Mats Hummels returned to Dortmund in one of the more intriguing transfers of the summer.
Having controversially joined rivals Bayern in 2016, the towering defender is back at the Westfalenstadion and Subotic believes it is a good move for both parties.
"I congratulate him. The team will benefit from him. He won four titles at Bayern during the last three years, while Dortmund only won one during that period. Dortmund will get a lot of experience in Mats. It is a big chance for him."
After backing his former defensive partner to be a success, he dismissed Bayern's claims that Hummels departed because he was scared of fresh competition.
"It is normal a club communicates it that way," he said. "Who is in this business for a ling time knows, that it has something to do with your ego."
Synonmous with Dortmund's iconic and successful team of the early 2010s, Subotic was delighted to see him former manager Jurgen Klopp finally get his hands on the Champions League this year with Liverpool following BVB's heartbreaking final defeat to Bayern in 2013 at Wembley.
"Of course, Kloppo finally did it. 2013 in the final against Bayern we already came very close.
"Until now Klopp won the championship and the cup. Now he managed to win an international title of the highest level."