I thought it was the complete opposite.
Rotation, power and containment were obviously the training required for a Rasengan, so he was bound to whip that out sometime. I actually thought he'd rasengan that guy's arm off, so I was pretty surprised when he just went "poof".
It explained my previous questions too as to how he'd pull off a Rasengan without clones. He didn't.
Now the question lies in whether Naruto's clone can gather and send Natural energy back to him, or whether he himself has to do it while his clones act as a diversion.
By far the first would be the preferred option, but guess we'll have to wait and see.
I guess from the frog's reaction, all sages in the past have used a frog to charge during combat.
What was the reason why you can't transform beforehand, or remain permanently in sage mode again?