Remember that in canon, being physically able and trained can only help but is not required. Morphing makes you stronger and faster, and gives an inherent, yet basic understanding of hand to hand fighting. Niberian's were never a very strong species because of their ocean homes, but the very long stasis period has rendered their bodies weak. The oldest ones cannot leave their pods at all, and instead act as overseers.
This was another reason the Nova Coin was made to be 'slow burning', so that you would never need to demorph. Of course, the Niberian Ranger would be young, both in age and in stasis time. He'd be the same kind of weak as a scrawny teenager would be, but mostly in muscle mass. The stasis wouldn't have dulled his body by much yet, so out of Nova Form, he'd be in trouble, but not in an "Oh God, can't stand up, falling over now!" way.
Hope that helps.