Samoa are counting the cost of their 49-12 victory over Namibia, after two key players were injured in a rugged Pool D match in Rotorua on Wednesday.

Flyhalf Tusi Pisi (left hamstring) and blindside flank Taiasina Tuifua (rib) were forced off the field after 30 minutes against a Namibian side who remain winless after 13 World Cup matches.

Samoa coach Titimaea Tafua said it was too early to assess the damage, but he will be especially concerned for Pisi, a left-foot kicker who had bagged 10 points before leaving the field.

"The medical people are still working on it," said Tafua, who rested several key players in the second half to avoid any more serious injuries.

"We'll know more later. I do hope it's not serious."

Tafua and his players will have their fingers crossed as they have just four days to prepare for a crunch match against Wales in Hamilton which is likely to decide who progresses to the quarterfinals.