Sportal.co.nz 19.May.2013Getty Images
Wallabies coach Robbie Deans names his preliminary 25-man squad on Sunday but will have to do without the powerful front-row forward.
Polota-Nau fractured his forearm tackling Henry Speight during the New South Wales Waratahs' 28-22 victory over ACT Brumbies on Saturday to miss out.
Deans told Fox Sports: "Tatafu right from the outset didn't look good, so he'll be
"You don't get the sort of opportunity the Lions series presents very often and it looks like he'll be denied that now so that's very disappointing for him and for us."
Veteran flanker George Smith has been tipped for a recall from international retirement, but his chances are now in the balance as well.
The flanker, who boasts 110 caps, injured his knee in the bruising Super Rugby encounter and was forced to limp off around the hour mark.
The 32-year-old had been giving rival Michael Hooper a masterclass in back-row forward play before incurring a suspected medial ligament injury.
Deans said: "It could be significant, but let's hope not because he's very keen to
"We only resolved his elegibility yesterday and he didn't look great when he left but if he's talking positively, that's a good start."
In terms of how he will set up his side for the Lions, Deans added: "You've got to attack to win, you've got to find ways to unlock teams.
"I think it's pretty evident what's going to be coming the other way. They're going to be direct, they're going to be physical.
"They'll look to squeeze the life out of us, play a territorial game and bring the ref into play."
Deans will add a further six players to his squad on June 11 after the Lions have touched down on Australian soil following the Barbarians game in Hong Kong.