User blog comment:Prophet of Sanghelios/Wild and Exciting Speculations!! Part 1!!!/@comment-452405-20100328075813

Yeah, I doubt Isshin is the type of person to jump in front of Aizen with a drawn sword and a grin without expecting to win. Either that or the personality we've seen him display to Ichigo carries over to his Shinigami attitude and he attacks randomly only to lose.

But then that'd be a stupid way to portray his abilities wouldn't it?