Colloquial contraction “出しゃ[あ]” [duplicate]

Question

I encountered this sentence.

なめんなよ。てめえみていな雑魚、おれが本気をだしゃあ…

I believe the context is quite obvious: The speaker feels stronger than his enemy, the listener. From how I understand it, I’d translate the sentence something like this:

Don’t make fool of me! Against a small fry like you, I don’t even need to fight seriously.

Still, I can’t figure out, how the ending works to carry this meaning. My guesses so far are:

• The trailing あ is just an emotional prolongation – the verb form is just 出しゃ.
• The しゃ is some kind of contraction like e. g. なきゃ. But what of? Perhaps something like 出しては?

If these guesses are correct, there is probably still a part of the sentence missing as an ellipsis.

Thus, my question is: What are the missing or contracted parts and how do they form the meaning inferred from the context? Or maybe I got it completely wrong and the sentence means something else?

Answer 1

出しゃあ is a contraction of 出せば. Compare すれば → すりゃ, 書けば → 書きゃ, 死ねば → 死にゃ, ..., that is //eba// → //ʲa//.

The extra あ could be seen as a lengthening to compensate for the lost mora. (See also 手えふった - what is the "え” here?)

Of course it means something like

おれが本気をだせば...
If I were to get serious...

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P.S. 出しては would usually contract to 出しちゃ

Answer 2

「Verb in Dictionary Form - u + ya」

makes the colloquial hypothetical form of the verb, which in the formal form, would be:

「Verb in Dictionary Form - u + eba 」

Thus, 「出{だ}しゃ」 is the colloquial form of 「出せば」.

「おれが本気をだしゃあ」, therefore, means "if I went all-out" with the whole main clause describing the result left unsaid. What is left unsaid would be something along the lines of "You won't last a minute."