The Hayne transition hasn't kicked off promisingly which is hardly surprising, since he's an absolute beginner up against blokes who have planned much of their lives around being NFL pros.
The Hayne leap is an almost impossibly huge one when you consider the lengthy growing pains players like Sonny Bill Williams and Brad Thorn needed making the familiar switch between league and rugby. Then there was Benji Marshall, who flopped completely.
Hayne must not only adapt his skills and learn a game with a huge playbook, but he will lack the instincts of Americans brought up on the game.
I would love for him to succeed and like many others was glued to the TV for his debut, but all it did was add to the mystery. The famous opening fumble in a tricky wind against the Minnesota Vikings wasn't the only problem.
He has only played a handful of matches, and it showed. He was fortunate in a way that his fumble was partly obscured by a mistake-ridden game, did not prove costly, and his team won.
However he was shown up by the speed and dynamism of the 49ers running back Carlos Hyde and punt returner Bruce Ellington. There was only one Hayne shimmy past a defender to cheer about, but in a sport of over-analysis opponents will learn the tricks of his trade.
Hayne has already done the unbelievable by making the 49ers squad, but he showed nothing better than must exist within 100s of American football players who are already deeply schooled in Gridiron.
The NFL is not a trial. That's why it's a struggle to work out what the Hayne selection does for the 49ers. Tomsula must see something very special in him to work on and to be fair, some reports of his debut made mildly optimistic claims. But the leeway given in rating such a raw rookie will only last so long.