Board Thread:Naruto Discussions/@comment-26773508-20150905054531/@comment-23887466-20150905092607

There is no plot hole. After Minato met the Masked Man, he predicted that this guy will be a threat to the whole world. Minato's idea was that in order to stop the Masked Man, the power of the Nine-Tails is necessary.

Kushina's Chakra was a special Chakra that allowed her to supress the Chakra of the Nine-Tails completely, this removed the possibility of her being able to utilize Kurama's Chakra in any possible way.

That's the reason Minato sealed Kurama in Naruto, hoping that one day Naruto will be one able to use the beast's Chakra in order to complete a certain jutsu, which most of us believe that he meant the Chakra Mode, in order to defeat the Masked Man.