To be clear, I am not asking about なか after a verb (which can mean "during"/"while"). While reading, I encountered:
You think you can definitely beat us!?
The speaker here generally speaks with a (stereotypical, borrowing from both 広島弁 and 大阪弁) western Japan accent (ie: だ->じゃ, だから -> じゃけえ, れば ->りゃあ, etc), so it's possible that this is something dialectical, but I can't find anything on it.