Well, with the recent developments seen in 434, Naruto can use shadowclones to temporarily gain their "state of mind" from sage mode, giving him quick bursts of it before it wears off. His time to make rasengans seems to be near-instantaneous in sage mode, so, if he were fighting Sasuke, then he would probably somehow factor this in (though the whole deal is to beat him, not kill him, and I have no idea how Naruto plans on doing that)