Since you brought it up...
I don't think nervousness is at all warranted with Mahuika returning. I haven't looked at his stats, but how many has he dropped.
No, not nervous. More like resignation to the fact that he'll most likely end up less than ten yards from where he caught the ball. Mahuika is really fast--on a track. But on the field his speed is swamped by his indecisiveness. Collie excels because he quickly takes a read and goes with it. Mahuika needs about a step more to accelerate to his top speed, and combined with his second guessing himself, he rarely reaches that speed.
Course with all of his injuries, it's understandable that he'd be a little gun shy and second-guessing his decisions.