"I'm really excited we won because Angie and I are officially the worst doubles team ever!" Petkovic said. "Up until Stuttgart we hadn't won a match, but there we made the semis and were actually quite good!
"We just connect so well and have a really great chemistry going on so I think that makes up for our, let's say, less than great doubles skills."
Their next outing after Stuttgart came at the French Open where they were brushed aside in straight sets by Black and Erakovic. It was clear from the outset, though, that the rematch in Cincinnati would be a more competitive affair.
Both sets followed similar patterns, with Black and Erakovic forging ahead - they served for the first and held three set points in the second - before being pegged back and then pipped on the tie-break.
"It was a close match and very tough," Kerber added. "They are a very good team, so we just went out there to have fun and we ended up playing very well together!"
In the second round, Kerber and Petkovic will face No.4 seeds Andrea Hlavackova and Lisa Raymond. Also advancing were No.6 seeds Anna-Lena Groenefeld and Kveta Peschke and No.7 seeds Chan Hao-Ching and Katarina Srebotnik, who scored straight set wins over Janette Husarova and Monica Niculescu and Shuko Aoyama and Chanelle Scheepers, respectively.