User blog comment:Omega natsu2/Chapter 372: Breach, Predictions./@comment-33019320-20140219094024/@comment-4800978-20140221091344

I'm not getting my information from a databook or the wiki, so don't base your points around assumptions. Instead I'm getting it from an understanding of the series and the multiple occasions where the Rasengan has clearly been shown as self-sustaining - rather than relying on a single example during the training of the technique which was only relevant over a decade ago.

The Rasenshuriken, while using the Rasengan as its base technique, is still an entirely different ability as it involves several more complicated steps such as form manipulation and implementing wind-natured chakra. And with the advent of Sage chakra (another thing Minato can use) that flaw in the technique has been negated.