The Citizens were unable to find a way past their Championship opponents after 90 minutes plus extra time, being taken all the way to a penalty shootout at the Etihad Stadium.
Guardiola criticised the 'unacceptable' quality of the ball, but was full of praise for back-up stopper Bravo after producing a number of big stops prior to the shootout.
"The ball is bad for one year or two years - it's not acceptable. All the players complain," he told reporters. "Claudio gave us the chance to go through - I'm so happy for him, the way he's trained, a good performance and good penalties. I'm happy to win in this way.
"It was not easy last season for him but he's a keeper at a high level – you can't be the Barcelona and Chile [goalkeeper] without being a high level. He deserved the performance. Without him we would not be in the next round."
"It's not easy for him, like with Yaya [Toure] he wanted to touch the ball but it's difficult because the space was tight. For Claudio he's here to play but he's a good professional and he has to be ready - you never know what happens in football. But it's not easy to come in for games like this."
The ball used was introduced at the start of the campaign for all EFL competitions, except for the Premier League.