I found the following sentence in a Japanese textbook:
"明日の試合に勝ちたいなら、きっと練習しなければ。 If you want to win tomorrow's game, you must practice."
This was in a section to do with なら, there was no explaination provided regarding the second half of the sentence. However the second half confuses me. Why does 練習しなければ mean 'must practice'?
I understand that 練習しなければ is the negative conditional form of 練習する, which should mean "If I don't practice" or "unless I practice". Is this just an additional way to use this form (i.e. the negative conditional form for X can also mean 'must X')?
Is this a shortening of 練習しなければならない? This makes sense to me, but I can't find any info online that suggests it's grammatically correct to shorten/contract '練習しなければならない' in this way.