Brian O'Driscoll will miss Ireland's opening World Cup match after suffering a fractured sinus in a 42-6 warm-up win over French side Bayonne on Thursday.
Irish skipper Brian O'Driscoll receives treatment for the injury
The 28-year-old captain was taken to hospital with a suspected broken right cheekbone after an apparent punch by Mikaera Tewhata in the second half.
But X-rays have revealed the injury is not as bad as first feared.
He will miss Ireland's final warm-up match against Italy and their World Cup opener against Namibia on 9 September.
"Following an X-ray and scan of Brian O'Driscoll's injury, it has been confirmed that he has sustained a fracture to his sinus and a deep laceration under his right eye," said an Irish Rugby Union statement.
I haven't the words to describe what I feel, I want to know what happened
French Rugby Federation president Bernard Lapasset
"This is not as serious as initially feared and the injury will not require any surgery.
"The recovery period for the injury is three to four weeks which will rule O'Driscoll out of the warm-up game against Italy next week and the first World Cup pool game against Namibia."
The loss of Ireland's inspirational leader against minnows Namibia should not be a major problem, while their second match, against Georgia on 15 September, should also be won with some comfort.
But coach Eddie O'Sullivan will be desperate to have O'Driscoll fully fit for the crunch pool games against France on 21 September and Argentina nine days later.
There was better news for O'Sullivan concerning number eight Denis Leamy, who suffered a shoulder injury in the match but it is not serious.
The injuries came in a bad-tempered game in France, which saw five players sin-binned.
Cedric Bergez and Ireland's Neil Best were yellow-carded in the first half while Bayonne full-back Daniel Larrachea and South African lock Robe Linde followed after the break along with Gordon D'Arcy.
O'Sullivan said that the physical nature of Bayonne's game sometimes went too far.
"I don't mind physicality, but it was more than physical," he said. "There were some cheap shots, that's the pity, but that's the way they want to play it. We can't control that, we can only play our game."
And the French Rugby Federation (FFR) has vowed to open an inquiry following the incidents during the game.
"I haven't the words to describe what I feel," said FFR president Bernard Lapasset. "This should have been a festival of rugby in a full stadium.
Paul O'Connell on his way to scoring a try in the warm-up game
"Happily we sent an official delegate, a foreign referee. I want to know what happened. I will open an inquiry."
Ronan O'Gara set the tone for the match with a first-minute penalty and the Irish went further ahead seven minutes later when Paul O'Connell went over in the corner.
Hickie then gathered the ball on his own 10-metre line and evaded two challenges on his way to a brilliant try which O'Gara converted for a 15-0 advantage.
Ulster wing Andrew Trimble scored Ireland's third try on the stroke of half-time while Hickie went over after the break.
O'Connell held off Larrechea's challenge to claim Ireland's fifth try before Hickie completed his hat-trick.
Ireland: Dempsey; Trimble, O'Driscoll (capt), D'Arcy, Hickie; O'Gara, Stringer; Horan, R Best, Hayes, O'Callaghan, O'Connell, Easterby, N Best, Leamy.
Replacements: Sheahan, Young, O'Kelly, Quinlan, Reddan, P Wallace, Murphy.